n THE PROPERTY OF THE NEW YORK EYE AND EAR INFIRMARY. LIBRARY. SECOND AVENUE AND I3TH STREET. PRESENTED BY 2Dr.Tf.Z3 l\Toyes . ■* \ 4 Digitized by the Internet Archive in 2016 https://archive.org/details/eye01fran i vjjVLVt : y Ij £> 7 A JnfMyz THE EYE 8 SCreatt'ge ON THE ART OF PRESERVING THIS ORGAN IN A HEALTHY CONDITION, AND OF IMPROVING THE SIGHT; TO WHICH IS PREFIXED, A VIEW OF THE ANATOMY. AND PHYSIOLOGY OF THE EYE; WITH OBSERVATIONS ON ITS EXPRESSION AS INDICATIVE OF THE CHARACTER AND EMOTIONS OF THE MIND. BY J. CH. AUGUST FRANZ, DOCTOR OF MEDICINE AND SURGERY OF THE UNIVERSITY OF LEIPSIC ; HONORARY MEMBER OF THE SOCIETY FOR NATURAL AND MEDICAL SCIENCES OF DRESDEN ; FELLOW OF THE MEDICAL SOCIETY OF LEIPSIC; AND ASSOCIATE MEMBER OF THE SURGICAL SOCIETY OF IRELAND. LONDON : J. CHURCHILL, PRINCES STREET, SOHO; CARFRAE AND SON, EDINBURGH ; AND IIODGES AND SMITH, DUBLIN. MDCCCXXX1X. folds. Printed by John Scott, 62, John Street, Holland Street. Blackfriars Road. i TO SIR BENJAMIN COLLINS BRODIE, Bart., F. R. S., Sergeant-Surgeon to the Queen, Surgeon to St. George’s Hospital, fyc. fyc. fyc. Sir, The motives which have influenced me in requesting permission to dedicate this Essay to you are — the respect due to your great talents and high scientific attain- ments, and a feeling of deep gratitude for the instruction and practical advantage I have derived from the perusal of your various writings. IV DEDICATION. To have favoured me with that per- mission, by which I am enabled to pay you this public tribute of respect and gratitude, is at once an evidence of a liberal and impartial spirit, a proof of genuine kindness of feeling, and an ho- nour conferred upon the following pages which I can never too highly appreciate. I have the honour to remain, with sentiments of profound esteem, Sir, Your most obliged and obedient servant, J. CH. A. FRANZ. P REFAC E. It is the duty of the medical man to labour not only for the cure, but also for the prevention of disease, and to use his best efforts for the preser- vation and improvement of the health of his fel- low-men. With a view to the fulfilment of this duty, as regards a most important organ in the human frame — namely, that of sight, the master- work of creation, — I have entered upon the com- position of the following Treatise, my chief object having been to point out the principles by which the organ of sight is preserved in a sound and healthy condition. In accordance with this object, commencing with the age of childhood, and proceeding through the successive periods of life, I have considered the circumstances peculiar to each period, and called attention to whatever is calculated to prove either beneficial or injurious to the eye. I have more- over given instructions as to the steps that should be taken in the incipient stage of diseases 6f that b VI PREFACE. organ ; but I have forborne to introduce into these pages any prescriptions for ophthalmic medicines, being of opinion that medicinal remedies in the hands of persons unacquainted with the principles of medicine may be compared to knives in the hands of children. In order to be better understood on the various points which the subject under consideration em- braces, and to give some idea of the wonderful structure of the eye, I thought it necessary to fur- nish at the same time an outline of the anatomy and physiology of this organ. While occupied with this purpose, many other ideas suggested themselves to my mind, which, — under an impres- sion that they might afford a proof of the dignity and importance of the organ of sight, and of its power of indicating the character and emotions of the mind, — I have presented to the reader, in the third and fourth Chapters of the first part of this volume ; for these two Chapters therefore I must apologise, as not strictly belonging to the subject in hand. Thus it has happened, that the observations which I at first wished to prefix merely as an introduction to the principal object, have increased under the pen so much beyond PREFACE. Vll my original intention as to form a considerable portion of the present work. The nature of my design in the composition of this Treatise has made it incumbent upon me to confine myself to general views without enter- ing into minute details, in order that I may be understood by readers not of the medical profes- sion ; and I ought perhaps to add, that for the same reason I have been compelled to pass over one or two specific affections of the eyes wholly without notice. While I beg that this may be kept in mind, — well knowing how much I venture in sending into the world an essay in a language not my own, I solicit the indulgence of the public towards the work which I now submit to their judgment. THE AUTHOR. 19, Golden Square, October 28, 1839. EXPLANATION OF THE PLATE. The figure represents a horizontal section of the an- terior part of the head, made in the direction of a line passing through the middle of the anterior aperture of each orbit, so as to show the form of the orbit ; the posi- tion of the eyeball ; the arrangement of its muscles ; the lacrymal organs ; the interior structure of the globe ; the course of the optic nerve ; and lastly, the formation of the image of an external object on the nervous mem- brane of the eye by means of the rays of light. In order to show the most important parts of the eye more dis- tinctly, the vessels and nerves have been omitted in this figure. 1 . The lateral walls of the orbit : the superior wall of the left orbit is entirely removed, but a portion of this wall is left towards the posterior part of the right orbit. (See page 3.) 2. The left eyeball with five of its muscles ; the sixth, being situated at the inferior wall of the orbit, is hidden by the globe. 3. The superior straight muscle. 4. The inferior — f>. The exterior — — 6. The interior — — c ^ (See page 11.) X EXPLANATION OF THE PLATE. 7. The superior oblique muscle, with its tendon pass- ing through a loop of cartilage, which is affixed to the foremost part of the upper wall of the orbit, where this wall unites with the interior wall. (See page 11.) 8. The lacrymal gland. (See page 12.) 9. The conjunctiva, covering a portion of the anterior hemisphere of the globe, and also the interior surface of the eyelids. (See page 5.) 10. Small orifices (puncta lacrymalia) through which the tears pass into the lacrymal ducts. (See page 5.) 1 1 . A transverse section of the lacrymal ducts. (See page 5.) 12. The ophthalmic artery, as it enters the orbit by the foramen opticum. 13. A horizontal section of the right globe. 14. The sclerotica. (See page 6.) 15. The cornea. (See page 6.) 16. The choroid. (See page 8.) 17. The dark pigment. (See page 9.) 18. The retina. (See page 8.) 19. The iris, having the pupil widely open. (Sec page 6.) 20. & 21. The anterior and posterior chambers, con- taining the aqueous humour. (See page 7.) 22. The lenticular system. (See page 7.) 23. The vitreous body. (See page 8.) 24. The central artery. (See page 11.) 25. The optic nerve, enveloped in its sheath. (See page 9.) 26. The chiasma of the optic nerves, a longitudinal section of which is made, to show the numerous fibrils EXPLANATION OF THE PLATE. XI composing these nerves, their course, and decussation. (See page 10.) 27. The part of the optic nerves coming from the brain. (See page 10.) 28. An object which reflects the light in the direction of the lines drawn from the points a to the eyes directed towards the object, just as every other point in the object would do. The lines b are pencils of light, as they find entrance through the pupil into the interior of the eye- ball, where each of them is by refraction made to con- verge to a point, called the focus, which, falling exactly on the retina, forms a distinct image thereon of the point a of the external object from which the pencil of light emanated. (See page 21.) This is what takes place at least in the eye in its normal state (See page 23) ; but when there is any deviation from this state, and the condition of the eye is such as to bring the rays of each pencil of light to a focus at the fine c or d, no distinct image can in this case be formed on the retina ; since, when the focus occupies the place of the line c, the rays in meeting the retina are again divergent ; and, when the focus is situated at the line d, the rays in meeting the retina are not yet brought into union with each other. The first case occurs in a near-sighted, and the second in a far-sighted eye. (See page 168.) The lines e repre- sent only the principal rays of each pencil of light re- flected to the left eye. CONTENTS. PART THE FIRST. ANATOMY AND PHYSIOLOGY OF THE EYE ; IMPOR- TANCE AND DIGNITY OF THIS ORGAN ; AND ITS EXPRESSION AS INDICATIVE OF CHARACTER. CHAPTER I. ANATOMY OF THE EYE. Page The orbit, and lacrymal canal . . . .3 The exterior soft coverings of the eye ; and the lacrymal duct ....... 4 Structure of the eyeball ..... 6 Nerves and vessels of the eye . . . .9 Muscles of the eyeball ; and lacrymal gland . .11 CHAPTER II. PHYSIOLOGY OF THE EYE. Introductory observations . . . . .13 Eyelids ; and lacrymal functions . . . .15 Eyebrows and eyelashes . . . . .16 The act of vision. §. 1. Objective vision Light, three of its laws . . . .17 Application of these laws to vision ; formation of the image on the retina . . .20 Iris, pupil, and dark pigment . . .24 d XIV CONTENTS. Page §.2. Subjective vision Seeing, a mental act . . . .26 Distinction between sensation and. idea . . 29 Visual sensation . . . . .31 Visual perception . . . .32 Ideas of visible objects, as arising without the pre- sence of the objects . . .36 Seeing, an art acquired by exercise and experience 39 Objects seen in their true position, though the image is inverted on the retina . .42 Vision single with a double organ of sight . 44 CHAPTER III. IMPORTANCE AND DIGNITY OF THE EYE, AND ITS PRE-EMINENCE ABOVE THE OTHER ORGANS OF SENSE. §. 1. Comparison of the sense of sight with the other senses . . . . .47 §. 2. Language of the eye . . . .54 §. 3. Power of the glance . . . .57 §. 4. The eye in relation to the countenance . . 59 §.5. Form and nature of the eye . . .62 §.6. The eye a microcosm . . . .65 §. 7. The eye a micanthropos . . . .69 CHAPTER IV. EXPRESSION OF THE EY'E AS INDICATIVE OF CHARACTER. Observations on the look and its principal differences . 73 Section I. — Expression of the eye with reference to the quality and condition of the mind. §. 1. Indication of the innate constitution of the mind The eye of the man of powerful understanding . 82 The of the man of impassioned feeling . 83 The eye of the man of energetic volition . . 84 CONTENTS. XV Page The eye of the man of talent, and creative genius 84 The eye of the man of limited capacity . . 86 §. 2. Indication of the habitual disposition of the mind a. ) The moral condition ., . . .87 The eye in virtue and piety . . .87 The eye in innocence . . .88 b. ) The immoral condition . . .88 The eye in immorality . . .89 The eye in vice . . . .89 §.3. Indication of the emotions of the mind a. ) Affections . . . .90 The eye in love . . . .90 The eye in unsuccessful love . .91 The eye in hatred . . . .92 The eye in joy . . . .92 The eye in sorrow . . .93 The eye in hope . . . .93 The eye in despair . . . .94 The eye in fear . . . .94 b. ) Passions . . . . .95 The eye in terror and horror . . 95 The eye in anger and revenge . .95 The eye in envy and jealousy . . 96 Section II . — Expression of the eye at the different periods of life . . . .99 Section III . — Expression of the eye as influenced by difference of sex . . . 102 Section IV . — Expression of the eye in reference to the moral and intellectual condition of nations. .... 105 APPENDIX : OR PRACTICAL OBSERVATIONS ON THE EXPRESSION OF THE EYE, ESPECIALLY OF THE LOOK. Study of the look important to metaphysicians and moralists 109 Study of the look important to members of the legal pro- fession . . . . . .125 XVI CONTENTS. PART THE SECOND. ART OF PRESERVING THE EYE IN A HEALTHY CONDITION, AND OF IMPROVING THE SIGHT: MANAGEMENT OF OPHTHALMIC DISEASES IN THEIR INCIPIENT STAGE. Page Introduction ...... 133 CHAPTER I. THE EYE IN INFANCY. Management of the infant in reference to the eye . .136 Ophthalmia of new-born children . . . 139 Squinting ...... 143 CHAPTER II. THE EYE IN CHILDHOOD. Management of the child in reference to the eye till the end of the second dentition . . . .130 Small-pox, and other violent eruptive diseases . .152 Remark on Dr. Jenner and Vaccination . . . 155 Struma, and strumous affections of the eye . . 155 Mental education . . . . .162 CHAPTER III. THE EYE IN YOUTH. Management of the organ of sight . . .166 Explanation and difference of near-sightedness, far-sight- edness, and weakness of sight . . .168 Near-sightedness, or myopy . . . .171 Certain sources of injury, as stays, tight cravats, tobacco- smoking . . . . . .178 CONTENTS. XVII CHAPTER IV. THE EYE IN MANHOOD. Page Management of the organ of sight . . .181 Dependence of ophthalmic diseases on general disorders . 182 Catarrh; rheumatism; gout . . . .184 Disorders of the abdominal organs ; fulness of habit ; con- gestive state of the head . . . .184 Chronic eruptions; open sores; swellings; haemorrhoids . 185 Ophthalmic complaints as connected with the peculiar con- stitution of the female sex . . . .186 Complaints of the eye occasioned by violent emotions of the mind ...... 189 CHAPTER V. THE EYE IN OLD AGE. Management of the organ of sight . . .191 Far-sightedness, or presbyopy .... 193 Weakness of sight; muscae volitantes . . . 195 Amblyopy, and Amaurosis .... 202 Cataract ....... 206 Observations on some other complaints of the eyes . 211 CHAPTER VI. GENERAL REGIMEN WITH REFERENCE TO THE EYE. Section I. — Management of the whole body. Air and exercise . . . .213 Attention to the skin . . . 214 Conduct in reference to the abdominal organs 215 Conduct in reference to the brain and nervous system .... 216 Conduct in reference to the vascular system 216 XVUl CONTENTS. Page Section II. — Adaptation of light to the eye. Strong light . . . .217 Weak light ..... 220 Abrupt changes in the degree of light . 221 Quality of light .... 222 Judicious regulation of light . . 224 Dwelling-houses, apartments, furniture, &c. 227 Section III. — Proper management of the visual function. Conduct in this respect . . . 232 Pernicious print and paper . . 235 Recreations for the sight . . . 236 Section IV. — Eye-glasses ; their selection and use. Nature and properties of good glasses . 239 When the near-sighted person should have recourse to glasses ; and how he should proceed in their choice and use . 245 When the far-sighted person should have recourse to glasses ; and how he should proceed in their choice and use . 252 Cataract-glasses . . . .254 Coloured glasses .... 255 Spectacles to defend the eyes against dust, Sec. “ Preservers,” and squinting spectacles . 260 Section V. — On certain sources of injury indirectly affect- ing the eye. Stimulants to the organs of taste and smell . 262 Articles of luxury, as cosmetics, &c. . 266 Section VI. — On certain sources of injury directly affect- ing the eye. Injuries from agents acting chemically or mechanically .... 268 Contusions and wounds . . .271 Section VII . — On certain disorders of the eyes, and dis- eases of the body with reference to the eye. Redness of the eyes; specks on the cornea 273 Twitching and quivering of the lids; stye . 275 CONTENTS. XIX Page Redness of the edges of the lids ; puro- mucous ophthalmia; Egyptian ophthalmia 277 Disorders of the lacrymal organs . 286 Treatment of the eye in diseases of the body 286 Section VIII. — Prevention of those complaints of the eye which owe their origin to the various occupations of life. Precautions to be observed by literary men and artists .... 288 Precautions to be observed by workmen employed in manufactories, &c. . 289 Section IX. — Caution against empiricism and the use of nostrums in diseases of the eye . ,291 PART THE FIRST ANATOMY AND PHYSIOLOGY OF THE EYE ; IMPORTANCE AND DIGNITY OF THIS ORGAN AND ITS EXPRESSION AS INDICATIVE OF CHARACTER CHAPTER I. ANATOMY OF THE EYE. In this chapter I shall present to the reader a brief and general view of the structure of the eye, de- scribing its several parts and appendages, their re- lative position, and the purposes, so far as they are mechanical, which they are intended to fulfil. To defend and secure the eye, the noblest and most delicate of the organs of sense, from external injuries, the all-wise Author of nature has so formed the face, that the projecting bones of the forehead, nose, and cheeks, form, as it were, a wall or rampart, which in conjunction with some other bones of the head, seven in number, is continued backwards in such a manner as to form a deep, firm, and conical cavity, of about an inch and three quarters in depth, which is named the orbit or socket of the eye. In this socket lies the eyeball, with its muscles, vessels, and nerves, imbedded in adipose substance. At the posterior or pointed part of the cavity is found a round hole foramen opticum), together with two fissures which run to- wards the fore-part, and by which the different nerves and blood-vessels enter the cavity. At the inner edge of the orbit, quite close to the nose, 4 ANATOMY OF THE EYE. there is an excavation or groove, forming the opening of a canal, which runs down in a perpen- dicular direction into the interior of the nostril, affording a channel or outlet for the tears, and thence named the lacrymal canal. The anterior and wider opening of the orbit is closed by parts of soft texture, so that the eye-hall is covered and protected in front likewise against external injuries, as instanced, more particularly, in sleep. These soft parts are divided in the middle by a horizontal slit into two moveable parts, which form the upper and lower eyelids. The skin of the face is continued over the eyelids, from the free edges of which the eyelashes shoot forth. That portion of the skin, which is continued from the forehead over the upper and most prominent edge of the orbit, is planted more or less thickly with hairs, forming the eyebrows ; and in the same situation, underneath the skin, is found a muscle * which moves and corrugates the eyebrows. Beneath the skin of the eyelids there is a flat circular muscle, the office of which is to close them ; hut as the upper lid is larger than the lower, and endowed with greater mobility, and some power is required for its elevation, it is provided besides with an ex- * A muscle consists of a great number of fleshy fibres, united together by cellular tissue into a fascicle, which is surrounded by a delicate membrane, and is interspersed with nerves, blood-vessels, and absorbents. It possesses an inherent property of contraction and relaxation, and thus has the power of moving the parts to which it is attached. ANATOMY OF THE EYE. 5 elusive muscle of its own, which, rising at the back of the orbit near the foramen opticum, runs for- ward to the eyelid and serves to raise it. Beneath the circular muscle, both in the upper and lower lid, is placed a small cartilage, for the purpose of keeping the eyelids extended in their proper form. A great number of very small glands ( glandules Meibomiance ) are situated along the free edges of the lids. At the margins of the eyelids, near the eyelashes, the skin of the face changes its character, and be- comes a delicate lubricated membrane, which is continued over the internal surface of the lids, and also over the anterior visible part of the eyeball ; thus forming a connecting membrane, which has, accordingly, received the name of the conjunctiva . At the inner canthus or nasal angle of the eye, this membrane forms a small semilunar fold, near which lies a gland ( caruncula lacrymalis'), ap- pearing like a little red fleshy excrescence. In the neighbourhood of this little fold, at the free edge, both of the upper and the under eyelid, two little points or openings ( puncta lacrymaliaj are discernible. Through these openings the conjunc- tiva is continued in the form of two minute and delicate tubes, and, having formed the lacrymal sac and the lacrymal duct, which are situated in the bony canal, loses itself in the membrane that lines the interior of the nostril ; so that the mucous membrane of this organ is a continuation of the b 2 6 ANATOMY OF THE EYE. conjunctiva. Upon the lacrymal sac is found a little muscle which moves it, and thus propels the tears into the nostril. Through the continuation of the conjunctival membrane into the nostril, the organ of sight is brought into the most intimate connection with the organ of smell. In order to present us with a clear and lively idea of the construction of the organ of sight, the eye- ball, which is of a spherical form, and only a small part of which is perceived from without, may be not unaptly compared with a watch. The external coat or white portion of the eyeball is a very firm, tough, leather-like membrane, which makes up about five-sixths of its spherical surface, protects the more delicate parts composing the interior of the globe, gives it its form, and serves for the at- tachment of the muscles which move the eye-ball ; this corresponds to the outer case of the watch, and is named the sclerotica. Closely and firmly united with the sclerotica on the anterior hemisphere of the globe is a highly transparent membrane of a horny texture, which is thence named the cornea: it fills up the remaining sixth of the spherical sur- face of the eye-ball, and corresponds to the glass of the watch. The dial-plate is represented by the iris, which with its various shades and gradations of blue and brown, is seen clearly through the transparent cornea, as in the watch the dial-plate is seen through the glass. The iris is a circular membrane of peculiar texture, abounding in nerves ANATOMY OF THE EYE. 7 and blood-vessels, and is attached at its circumfer- ence by means of a dense texture, called the ciliary body, to the sclerotica, immediately behind the union of the latter membrane with the cornea, the rest of the membrane being loose and moveable. The iris has, nearly in its centre, a circular aper- ture, which is called the pupil. As in the watch there is an intervening space between the glass and the dial-plate, so also is there in the eye between the cornea and the iris ; but there is, moreover, behind the iris, a space similar to that in front of it ; the one is named the anterior, and the other the posterior chamber of the eye. Both these chambers are filled with a clear watery fluid, called the aqueous humour, having a communication through the pupil, which is constantly open. As the works of the watch lie behind the dial-plate, so also the most important parts of the organ of sight are found behind the iris. Close behind the iris and the posterior chamber of the eye, a gelatinous, very transparent body is situated. Its form is that of a lens, the diameter of which, in the human adult, is four Parisian lines, and its thickness at the centre two lines; it is named the crystalline lens. It is in- closed in a transparent, delicate, membranous cap- sule, between which and the lens a slight vapori- form moisture exists, called humor Morgagni; the whole, taken together, is termed the lenticular system. The anterior surface of this lenticular 8 ANATOMY OF THE EYE. system is moistened by the aqueous humour of the posterior chamber of the eye ; the hinder surface is imbedded in the vitreous body. This latter body consists of numerous small cells formed by the interlacing of a very delicate and transparent membrane, all of which are again inclosed in a fine investing membrane. Each of these cells is filled with a very clear and transparent fluid. The vitreous body constitutes about four-fifths of the contents of the eyeball ; the remaining fifth is made up by the lenticular system, the two chambers, and the iris. The whole of the vitreous body, with the ex- ception of the anterior part, in which the lens is imbedded, is surrounded by a thin transparent layer of nervous substance, named the retina, which converges to a point nearly at the centre of the pos- terior hemisphere of the eyeball, and constitutes the true sensitive portion of the visual organ, and the first link in the chain upon which the act of subjective vision * depends. Between the retina and the sclerotica is spread a vascular membrane, called the choroid coat, which is composed of a great multitude of arteries and veins, shooting both laterally and posteriorly into the eyeball, and dispenses warmth and nourishment to the eye. The internal surface of the choroid coat is of a dark- brown colour, occasioned by a pigment, commonly * Vide Chap. II. Sect. 2. ANATOMY OF THE EYE. 9 called pigmentum nigrum, with which the posterior surface of the iris is also covered ; for the same pur- pose as that for which the interior surface of every optical instrument is blackened, viz. to prevent reflection of the rays of light. The whole interior spherical surface of the eyeball is consequently hung, as it were, with dark tapestry ; on which account the pupil, serving as the sole avenue of light to the interior of the eye, appears black. The retina converges to a point, as has been already observed, in the interior of the eyeball, and at its posterior hemisphere, nearly opposite to the pupil. Here it loses itself in the nerve of sight or optic nerve, so that it may be regarded as the immediate expansion of this nerve. This nerve is composed of numerous fibrils, each inclosed in a fine membrane, and the whole enveloped in a membranous sheath : it issues from the sclerotica as a nerve of about the thickness of a common quill, and runs through the round hole at the back of the orbit before mentioned, quite through into the cavity of the skull. Immediately after the en- trance of the nerve into the skull, the nerves of both eyes meet and enter into a union of a very remarkable and important kind ; inasmuch as the inner halves of the two nerves cross each other, the inner half of the right nerve proceeding to unite itself with the outer half of the left, and the inner half of the left nerve with the outer half of the right, while the outer halves do not cross, but re- 10 ANATOMY OF THE EYE. main on either side of the point of union. To this crossing of the nerves the name of chiasma nervo- rum opticorum has been given. After thus uniting they are again separated, and appear as two dis- tinct nerves, the one pursuing its course on the right side, and the other on the left, towards the innermost part of the brain, with the most im- portant portions of which it amalgamates itself. The organization of these nerves differs from that of all other nerves, and is so peculiar, that the optic nerves must rather be regarded as a direct continuation of the substance of the brain to the interior surface of the eyeball, i. e. to the retina. A number of small nerves ( nervi ciliares ) penetrate the sclerotica from without, and run between this membrane and the choroid to the iris, while dif- ferent nerves go to the muscles and the rest of the parts surrounding the eyeball. All these nerves are derived from the brain, form communications with each other, and unite also with the great sym- pathetic nerve, which latter nerve is again intimately connected with the spinal chord. These direct or indirect communications with the different divisions of the nervous system are of the greatest import- ance, as the eye is brought by their means into the most intimate relation with the whole circle of sensation of the entire body. Nearly corresponding with the nerves, a number of arteries and veins run likewise to the eyeball and its surrounding parts. These vessels ramify ANATOMY OF THE EYE. 11 in various directions, and, in the choroid coat, pre- sent the appearance of net-work. The central artery takes a very peculiar course ; exteriorly to the eyeball, and at some distance from the sclero- tica, it inserts itself obliquely into the optic nerve, then runs through its centre, straightforwards, in the direction of the axis of the eyeball, and finishes by giving off some branches to the vitreous body, and to the posterior surface of the capsule of the lens. Here, as generally throughout the system, the arteries carry out a bright red blood to the parts with which they are connected, while the veins bring hack blood of a dark colour from those parts to the heart. Many of the vessels of the eyeball are of such delicacy that they are not to be distinguished in the healthy eye, but only be- come visible in disease. The apparatus for moving the eyeball consists of six muscles, four of which, the straight muscles, have their origin at the hack of the orbit round the foramen opticum, and are attached to the scle- rotica in antagonist directions, viz. above and below, and on either side, so that the one can move the eye upwards, the second downwards, the third to the right, and the fourth to the left side. The other two muscles, the superior and inferior ob- lique muscles, rising from the interior wall of the orbit, and attached also to the sclerotica, but in an oblique direction to the former, move or turn the eye round its horizontal axis. These six muscles not 12 ANATOMY OF THE EYE. only serve the purpose of moving the eye, hut also keep it firm and in its proper place in the socket. In the forepart of the orbit, towards the tem- ples, and near the eyeball, is situated the lacrymal gland, which has several minute orifices opening on the interior surface of the upper eyelid, through which the tears issue. The eyeball, with all its parts, lies in a soft bed of adipose substance, which fills up the whole of the interval between them and the orbit. CHAPTER II. PHYSIOLOGY OF THE EYE. By Physiology is understood the science which treats of the structure and functions of organized bodies, and more especially of the human body ; to this science, therefore, in furtherance of our design, we must have recourse for the explanation of the uses and functions of the various parts of the organ of sight, and of the mode in which vision is effect- ed by them. In the organization of the living body, the va- rious systems and organs of which it consists stand in reciprocal dependence upon each other. The activity of one system promotes that of a second, the functions of one organ stimulate those of an- other, and so forth ; so that the intimate con- nexion of all the actions and the successive series of all the functions constitute a perfect circle, which is termed organic life. This life has its ori- gin in the maternal bosom, but as soon as the human being has emerged from this obscurity into the light of the external world, the life of the senses is at this very moment awakened; and as the organic life was derived from the mother, so is c 14 PHYSIOLOGY OF THE EYE. the life of the soul developed from that of the senses through the contact and communication of man with the external world. Still it is but one power, the vis vitalis, the Evoggcvv of Hippocrates, which produced and which maintains this threefold life, which by degrees becomes more and more con- centred in the mind ; and thus the mind has, or is at least intended to have, the predominance, and to modify and determine the condition of man with regard to the world. — The contact of man with the external world is a reciprocal relation between the two, which in man consists, besides nutrition and assimilation, in sensation and voluntary motion. The action of the external world occasions sensa- tion ; this produces perception and an idea in the mind ; and again the idea is succeeded by a bodily movement, which has for its consequence an action upon the external world. Sensation is effected through the medium of the senses, and the organs of sense therefore are not merely nominally, but actually organs ; that is, instruments or means which the mind uses for its own purposes. — With regard to eternity and infinity, the soul is permitted to indulge in conjectures and aspirations only; but all ideas connected with time and space are the result of a contact and intercourse betwixt the soul and the external world, as is proved by every operation wherein one or more of the senses are implicated, although we are just as little able to PHYSIOLOGY OF THE EYE. 15 understand the nature of that contact and inter- course as we are in a condition to investigate the nature of the soul itself. To return after this digression to the sense of sight, let us represent to ourselves an individual with his eyes closed, in whose mind the desire of seeing any external object has arisen. In this case the faculty of the mind which is first called into action is the will ; this excites muscular motion, which is followed by a series of functions and ac- tions in rapid succession. At the moment of vo- lition the eyelids first open through the influence of the nerves upon the muscles, the eye moves and directs itself towards the object which the mind wishes to view, and several changes are occasioned in the interior of the eyeball by the stimulus of light. The external world has now become visible to the individual, and he is therefore placed in a condition, as far as regards the objects themselves, to occupy himself with the things around him, and to act upon them according to his subsequent will. Thus the eyelids may be compared to a pair of curtains hung between the mind and the external world, which they alternately unfold to, or veil from the view. But they serve likewise as a defence against external injuries, whose influence they keep off during sleep, as also while we are awake, by closing quickly, for instance, on the approach of any small insect. As these sources of injury, such as particles of dust, &c., enter the eye for the most 16 PHYSIOLOGY OF THE EYE. part from above, the upper lid is the larger, and has moreover a wider compass of motion. The opening and closing of the eyelids, together with the motions of the eyeball, exercise a stimulus upon the lacrymal gland, which augments the se- cretion of its fluid in the neighbourhood of the outer canthus of the eye and on the inner surface of the upper lid. This fluid is then diffused by the act of winking over the whole of the anterior hemisphere of the eyeball. It is this which gives the eyeball its lustre, moderates the effect of noxious airs, keeps it cool by its constant and partial evaporation, and, lastly, facilitates the motion of the eyelids. After having fulfilled this office for the eye, it collects itself in the inner canthus of the eye, which for this purpose is of a semilunar form. Here, after being mixed with a peculiar fluid secreted by the caruncula lacry- malis, by which it is rendered milder, it is absorbed by the puncta lacrymalia, and carried through the lacrymal duct into the nostril, where it has a new office to perform. When the lacrymal gland is excited by any external cause, or rendered more than ordinarily active by any affection of the mind or body, it secretes a greater quantity of this moisture than the puncta lacrymalia are able to absorb, in consequence of which the fluid runs down over the cheek in the form of tears. The eyebrows and eyelashes, besides serving as ornaments to the face, and contributing to the PHYSIOLOGY OF THE EYE. 17 expression of the mental character and emotions, as portrayed by the eye, have also for their object to shade this organ, and by this means, es- pecially when the former are contracted and bent down, moderate the stimulus of light when too strong for the eye. Besides this, they prevent the condensed perspiration which flows down from the forehead, and particles of dust or other substances floating in the air, from entering the eye. For this reason well-formed eyelashes, when the lids are closed, as in sleep for instance, are locked into each other, in the same manner as the fingers when the hands are folded. We may now proceed to consider the sense of sight, first, under the head of objective vision, i. e. an optical process dependent upon the exter- nal world, together with the visual apparatus ; and secondly, under the head of subjective vision, i. e. a mental act, dependent upon the mind, together with the optic nerve in its whole extent. § 1. Objective Vision. The first necessary condition for objective see- ing, diffused universally throughout nature, is light — for where there is no light there is no vision; the second is the visual apparatus, by which is to be understood the transparent media, c 2 18 PHYSIOLOGY OF THE EYE. the iris, and the pigmentum nigrum. It would he foreign to our purpose to enter into a minute investigation of the laws of light ; but there are three of those laws which claim our attention in this place ; first, as to its transmission ; secondly, as to its colour ; and thirdly, as to its refraction by transparent media. I. Certain bodies in nature are self-luminous, such as the sun, and all terrestrial bodies during combustion. From these light is emitted, and spreads itself in all directions in straight lines, commonly called rays. When any of these rays reach our eye directly or immediately, we see the luminous body itself. When any of the rays ar- rive at the surface of an opaque body, they are intercepted, and partially reflected according to certain optical laws, viz. at the same angle as that of their incidence, and the opaque body is now illuminated, and for the sake of distinction is called a non-luminous body. When the rays of light thus reflected reach our eye, the illuminated body becomes visible to us. II. Light, or rather every ray of light, consists of three primitive colours, blue, yellow, and red. If the surface of an illuminated object be of such a nature as to reflect the ray of light with an equal mixture of these three colours, it will appear white, and the more equal and intimate the mix- time, the whiter will be the colour. If, on the contrary, the illuminated surface be of such a PHYSIOLOGY OF THE EYE. 19 nature as to decompose the ray and separate either of the three primitive colours ; if now it attracts two of these colours to itself, or in other words, absorbs them, it appears of the third, or remaining colour, which not having been absorbed is re- flected : for example, if the blue and yellow be absorbed, the object appears red. But if the object have the property of absorbing one only of the primitive colours, it will then appear of that colour which results from a mixture of the two reflected colours ; if, for instance, the red be ab- sorbed, the colour of the object will he green, which results from the mixture of yellow and blue. From the respective degrees in which one or other of the primitive colours predominates in the mixture of the reflected colours, arise the infi- nitely various gradations and shades of colours, or light. Lastly, if the surface of the object possess the property of absorbing all the three primitive colours, it will then appear black, which will be the more deep and intense, the more perfectly and equally they are absorbed. The object in this case is, indeed, illuminated, but reflects no light. * III. When a ray of light falls upon any trans- parent body, such as water or glass, at right * A prism, as is well known, separates the ray of light both into the primitive and the mixed colours, which arrange themselves in the following order : — red, orange, yellow, green, blue, indigo, and violet. 20 PHYSIOLOGY OF THE EYE. angles to its surface, it proceeds straight through it in the same direction ; the ray is not intercepted by the substance. But when the ray falls ob- liquely upon the transparent body, it suffers re- fraction at the surface ; that is to say, it assumes on its entrance a somewhat different direction, which direction is maintained in its progress through the body, but on passing out of the latter is again changed. This property of transparent bodies is named their refractive power, which differs according to their various degrees of den- sity and combustibility ; the greater the density or combustibility, the greater the refractive power. * It is by the first two laws of light which we have adduced, that the external world and its various objects, with their infinitely diversified colours and shades, are rendered visible ; by the third, inasmuch as it is applied in the visual ap- paratus itself, the eye is placed in a condition to behold the external world and those various objects. * The following experiment affords an illustration of this law : Let a stick be held in a pretty good sized vessel filled with water in such a manner that the one half of the stick be immersed in the water. If the stick be held so as to form a right angle with the surface of the water, it will appear straight ; but if it be held obliquely, it will appear broken at the surface of the water, and will have apparently a different direction in the water. If oil be employed for the experiment instead of water, the appearance will be much more striking, on account of the greater density and com- bustibility of the oil. PHYSIOLOGY OF THE EYE. 21 From the first of these laws it is evident that some of the rays of light, whether proceeding from self-luminous, or from illuminated bodies, must reach the eye when turned towards the objects. These rays come in a diverging direction to the eye ; that is, they have the form of a cone, whose apex is at some point of the object, whilst its base is at the cornea of the eye. Such of them as find entrance through the pupil into the interior of the eye, proceed through its transparent media, viz. the aqueous humour, the lens, and the vi- treous body. These media differ from each other in density, which in all of them exceeds that of the atmospheric air; they have therefore a great refractive power, which is moreover considerably increased by the double convex form of the lens.* The effect of all this is, that the rays of light are necessarily refracted and made to converge in the interior of the eye. This convergence of the rays again presents a cone, whose point rests on the concave surface of the posterior hemisphere, i. e. on the retina, whilst its base is on the anterior hemisphere, i. e. on the cornea. The point on the retina is called the focus. The point of the ex- ternal object from which the rays diverge is thus * The effect of a lens, or common burning-glass is, as is well known, to collect the rays of light falling on its surface, and to unite them at one point, to which the Latin term focus (fire-place) has been applied, on account of a considerable degree of heat being produced at that place by the concentration of the rays of light, 22 PHYSIOLOGY OF THE EYE. truly represented through the refraction and con- vergence of the rays at the bottom of the eye, by a point exactly corresponding to that of the ex- ternal object. But since every point of the object sends rays to the eye in the same manner, these must accordingly present just as many foci on the retina, and as the points in the object lie close to one another, the foci at the bottom of the eye must also occupy exactly the same relative posi- tion among themselves, as those points in the ob- ject. Hence it follows, as a matter of course, that the object must form an exact image, though upon a greatly diminished scale, in the interior of the eye, namely, at the interior and posterior hemi- sphere, or on the retina, just as the picture of a landscape is presented on the table of the camera obscura. But, farther, it is an ascertained fact, * that this image is presented inverted on the retina ; and the reason of this inversion is, that the rays of light which come from the upper part of the object are refracted in the eye towards the lower part, those * Of the truth of this fact any one may easily convince himself. Let him take, for example, the eye of a white rabbit, from which the muscles and all the fat have been entirely removed, and let a lighted candle be held at some distance before the cornea. If the hinder hemisphere of the eye be now closely examined, an inverted image of the flame will be seen shining through the sclerotica, with its point directed downwards and its base upwards. In order to see this image distinctly, which shines through but faintly, the eye must be closely fitted into a hole bored in a tolerably large screen, by which means its posterior hemisphere is shaded and darkened. PHYSIOLOGY OF THE EYE. 23 coming from beneath towards the upper part, those from the right on the left, and those from the left on the right hand. If the construction of the eye he considered, it will he evident to any person ac- quainted with the principles of optics, that this must be the case ; its explanation belongs there- fore to that science. In a well-formed eye, that is to say, an eye whose construction is perfectly adapted to the purposes of vision, this image falls exactly upon the retina, and it is necessary that this should be the case, in order that a distinct perception may be produced upon the nerve. This exact coin- cidence is effected in the most perfect manner by means of the refractive media, the form of the eyeball, and extremely minute changes of its form, and no doubt of some of its internal parts. These changes are regulated according to the divergence of the rays of light, which of course varies with the distance of the object from the eye. This capacity of change is dependent upon the vital energy of the eye, a property which is truly worthy of admiration, but the intimate nature of which has not yet been sufficiently investigated. When there is any deviation from the normal state, either in the quality of the refractive media, in the form of the eye, or in its power of adjustment, the image does not fall exactly upon the retina. Hence arise short-sightedness and far-sightedness, both of 24 PHYSIOLOGY OF THE EYE. which will be treated of at length in the second part of this work. The quantity of the rays of light which enter the eye through the pupil, or the degree of light to which the interior of the eye is exposed, is by no means a matter of indifference for the organ of sight, with reference to the production of distinct vision. In strong light, the eye is acted upon in such a manner that the iris is expanded and becomes broader, in consequence of which the pupil is of course contracted, and becomes narrower and smaller. Weak light has an opposite effect.* In strong light, therefore, fewer rays enter the eye, owing to the contraction of the pupil, where- as, when the light is weaker, a far greater number are admitted by the dilatation of the pupil, so that the degree of light in the interior of the eye re- mains almost always the same, which is of import- ance for the distinctness of the image in the eye. Those rays of light which are not allowed by the iris to enter the eye, are reflected from the cornea and iris. From the capacity which the iris.pos- * The iris is not endowed with the power of voluntary motion, but may be influenced by other causes besides the stimulus of light; it may be excited, even when there is no alteration in the degree of light, by agents which affect the nervous system, as also by emotions of the mind. This is seen most evidently, for instance, in the eye of birds, under the influence of fear, terror, or anger ; and in parrots even a voluntary motion of the iris may he ob- served. PHYSIOLOGY OF THE EYE. 25 sesses of thus regulating the quantity of light admitted into the interior of the eye, it may be regarded as a photometer for the eye. And that it may answer this purpose still more perfectly, its posterior or interior surface is covered with a dark-brown colouring matter, which has been be- fore mentioned under the name of pigmentum ni- grum. This colouring matter is continued between the retina and the choroid coat throughout their whole extent, so that the interior of the eye is darkened, and the organ of sight in this sense be- comes a camera obscura. It was necessary that the interior of the eye should be dark or black, because this is the only colour adapted to prevent by its absorption of the rays any further change or re- fraction of the light, after the formation of the image upon the retina. The presence of this colouring matter on the posterior surface of the iris has, moreover, for its object, to prevent the light which meets its anterior surface from shining through it into the interior of the eye. The darker or lighter colour of the iris is owing to the greater or smaller quantity of this pigment which may be present, and dark eyes are enabled by it to endure a stronger light than those of lighter colour, although the latter can support more ex- ertion. The eye of Albinos accordingly is abso- lutely unable to endure bright light, because the dark pigment is entirely wanting. It will not be superfluous to recapitulate briefly D 26 PHYSIOLOGY OF THE EYE. the uses of the several parts of the eyeball. The sclerotica gives to the eyeball its form, and firmness for the attachment of its six muscles ; the choroid provides for its nourishment and warmth, the transparent media refract the light, and by causing the convergence of the rays form an image accord- ant with the object, which image is received by the retina ; the iris and the dark pigment moderate the light, and contribute to the distinctness of the image. § 2. Subjective Vision. From the foregoing description of objective see- ing the eye might well be regarded merely in the light of a highly perfect optical instrument, and the more so, as the refractive media form in fact no- thing more than what is called a compound lens. Now, as an optical instrument is only a means by which objects that are scarcely recognised by an unassisted eye, are rendered distinctly visible to it; so also is the organ of sight only an instrument or means through which the impression made by an external visible object upon that organ is perceived by the mind. The eye, when looking through an optical instrument, receives only the image of objects, and consequently remains merely passive; but the mind, looking as it were through the eye upon the external world perceives it, and thus is active. By means of the eye there is an inter- PHYSIOLOGY OF THE EYE. 27 course established between the world without and the mind within, and the objects in that world when seen are, by the unlimited self-activity of the mind, perceived, compared, and determined. The eye then is an instrument of the mind, and the manner in which it is used by the mind con- stitutes subjective seeing. The necessary con- dition for this is, first, the energy of the nerve of sense throughout its whole extent, viz. both as the retina and as the optic nerve continued into the interior of the brain ; and, secondly, the self- activity of the mind. With regard to subjective seeing, there exists therefore the same relation between the mind and the nerve, as exists in ob- jective seeing between the external world and the apparatus of vision. Now, the apparatus of vision may in itself per- fectly fulfil its purpose ; that is to say, may ex- hibit an image of the object in the manner before described upon the retina, yet it does not follow that the eye must see the object ; as is the case, for instance, in perfect amaurosis, in which the image upon the retina is not wanting, but the retina itself is paralysed. The activity of the retina, therefore, which consists in its sensation of the image, is the essential condition necessary for seeing. The sensation of the image is carried on- wards from the retina through the optic nerve to the brain, and here, in the organ of the mind, the cause, which has produced the sensation, becomes 28 PHYSIOLOGY OF THE EYE. known ; or, in other words, the self-activity of the mind forms an idea of the object, which is now perceived. Since, now, in a perfect and cultivated sense of sight, seeing and perception are one and the same, the impression made by external objects upon the retina through the medium of the visual apparatus must occur simultaneously with the sen- sation of this impression, and with the idea formed by the mind of the cause which produces the im- pression ; that is, to effect perceptive vision all the functions of the sense of sight both as regards the eye and the mind must cooperate and concur. Seeing therefore is in effect nothing more than a mental touching * at a distance through the me- * I use here the term touching, because there is in several points of view a great sympathy between the sense of sight and that of touch, or general perception, as is proved by the fact, that whenever the one sense is highly developed, it is always at the ex- pense of the other ; where the sight is acute, the sense of touch is obtuse, while on the other hand, when the power of vision is diminished in an extraordinary degree, the general perception is proportionally increased. Professor Juengken of Berlin related to me the following very interesting case of congenital night-blindness, which came under his own observation, and will serve to illustrate this point. A young gentleman, in good health, whose eyes had no organic defect, could see perfectly well in the day time ; but when evening came on, he was unable to distinguish more than the outlines of larger objects, and those but imperfectly, even when most brightly illuminated by gas or any artificial light. In proportion as his sight failed, his general perception acquired such a degree of acuteness, that he became sensible of the presence of every object which he approached, while at some distance from it ; and by this means was enabled to move about with security in crowded places. He described the sensation which he experienced PHYSIOLOGY OF THE EYE. 29 dium of the eye, and by the help of the rays of light ; and visual perception is the formation of an idea of the object gained from visual sensation. Now, however intimately this idea and this sen- sation may be blended with each other, and there- fore may appear at first view to be as one and the same, they are yet, on closer examination, consider- ably different in character and value. The difference is apparent of itself from the meaning of the words, if taken in their original and strict sense. Sensation is that state in which the mind merely becomes conscious of an impression made upon the body, especially upon the nerve. Idea, on the contrary, is a particular kind of thought, in which on approaching any object, as that of something pressing gently, or breathing upon him. On the return of day, his sight was again restored, and the sense of touch reverted to its normal state. The sense of sight, when lost, or when the necessary condition for its exercise — light — is wanting, is always in some degree com- pensated by the sense of touch. The blind man, for instance, endeavours to supply its deficiency by touching, and those who possess the faculty of sight have recourse to feeling when in the dark. Dr. Mackenzief relates a case of a child, whose eyelids had been closed continually for more than a year in consequence of a strumous complaint. “When the complaint had abated,” says he, “ the child groped with its hands, as if blind, although it saw; so strongly confirmed was the habit of using the sense of touch in preference to that of sight.” It has been frequently asserted that there exists the rudiment of an eye on the horn of snails ; in these animals therefore the eye would be at the same time an organ of touch and an organ of sight. In animals without eyes, feeling is substituted for the sense of sight. t Practical Treatise on Diseases of the Eye, Second Ed., page 453. D 2 30 PHYSIOLOGY OF THE EYE. something individual is conceived and understood by the mind. If now this individual object of thought be material, viz. excited through the me- dium of sense, the idea is derived from sensation. As soon as the sensation has produced conscious- ness, an idea is formed by reflection upon the sensation, and this constitutes perception of the material object in the mind. But now that such a difference between sensation and perception, as originally derived from sensation, does exist not merely in empty terms, but in reality, is manifest from the fact, that they sometimes occur not simultaneously with each other. When a person, for instance, is buried in abstract thought, the attention of his mind is withdrawn from impres- sions made on the organs of sense. Light through the open eye, sound through the open ear, produce each their proper impression, yet the individual neither sees nor hears, because the mind does not pay attention to the impression ; if, however, the mind be aroused from its reverie, that is, if its attention be called to the impression before the sensation of that impression is effaced from the nerve, the sensation produces consciousness, and an idea being formed in the mind, perception takes place. Thus it frequently happens in such cases that a suitable answer is given to some question which had been asked long before, to the great surprise of the inquirer. Thus also the mathema- tical calculations, in which the mind of A re lum e- PHYSIOLOGY OF THE EYE. 31 des was absorbed, prevented him from hearing the storming of Syracuse. An impression made on the retina or optic nerve places this nerve in a peculiar and active condition, which being felt by the brain is then perceived by the mind. This property of being placed in such a condition is termed its energy. When this energy is excited, the sensation of light is experi- enced. The difference in the quantity of excite- ment causes the sensation of the various degrees of light, viz. brightness and shade ; and the differ- ence in the quality of excitement gives rise to the sensation of the various kinds of light, viz. colours. If the excitement is totally wanting, the sensation of light will be also wanting, which state is that of darkness. The only sensation therefore which the optic nerve is capable of experiencing, consists exclusively in light ; for the sensation occasioned by visible objects is produced only through the medium of light. Now the activity of the optic nerve is most usually excited by the rays emanat- ing from a luminous body, but it may also be called into action by any other cause which stimu- lates that nerve. When the eyes, for instance, are placed in communication with the electric fluid, they perceive in the dark an appearance of light. Mechanical irritation, as pressure, or a blow upon the eye, produces the sensation of light. An in- jury so considerable as the cutting through the optic nerve, in the operation of extirpation of the 32 PHYSIOLOGY OF THE EYE. eye, often occasions a sensation as if large masses of fire were seen. The accumulation of blood in the vessels of the eye occasioned by a congestive state, or by inflammation of that organ, causes a pressure upon the optic nerve or retina which is perceived as an appearance of light or fire. Lastly, even the influence of medicinal substances, of narcotics, for instance, as foxglove, &c., when they are carried into the circulation excites the sensa- tion of a glimmering light before the eyes. I have said that visual perception is the forma- tion of an idea of a visible object gained from visual sensation. Since now a pure visual sensa- tion consists only in that of light, any idea merely derived from visual sensation can of course only exist with reference to light, viz. its degree and its kinds, and we may add, with reference to the extent of surface, when illuminated; for only in this case can the surface make an impression on the retina. We are able, for instance, to distinguish a triangular from a quadrangular surface by the sight alone; the idea, however, as far as regards the size of the surface, is subject to some deception, and therefore indefinite.* A definite and accurate idea con- * I must here advert to the question proposed by Mr. Molineux to Mr. Locke, which has been since frequently discussed, f namely, “ whether a person who had been born blind, and who had learned to distinguish a cube from a sphere by his touch, would, on acquiring the use of sight, be immediately able to tell the t Locke’s Essay concerning Human Understanding, Book II. chap. 9, $ 8. PHYSIOLOGY OF THE EYE. 33 cerning the bulk of a body, and its form according to its three dimensions, can only be formed by re- flecting on the impressions made both upon the sense of sight and the sense of touch. From the frequent seeing and feeling of things which are familiar to us, the two sensations become so inti- mately blended with each other, that on the re- currence of the objects to our view the sensation belonging to the sense of touch unites itself in the mind with that of the sense of sight, and it is not necessary for us to feel them again, but only to see them, in order to recognise them. But if we wish to have an accurate idea of the form of an object with which we are unacquainted, when presented to us for the first time, it is always necessary both to see and to feel it. Thus an un- practised eye will regard a globular body at a dis- tance as a mere disk ; feeling corrects the visual sensation, and thus by reflecting on both impres- sions the idea of the spherical form is obtained. Persons who have not been accustomed to view one from the other, before he touched them.” Both these gen- tlemen have answered this question in the negative, but it does not admit, strictly speaking, of being either entirely affirmed or denied. The supposed person will certainly be able to distinguish by his sight the cube from the sphere, though he will not, it is true, recognise the two figures as a cube and a sphere , but will pronounce the one to he a disk and the other a square ; it must be premised, however, that some little time must be allowed for the mind to recover from the confused sensation produced by the novelty and multitude of objects suddenly presented to the newly acquired faculty. 34 PHYSIOLOGY OF THE EYE. objects by reflected light, suppose the objects which they see by reflection to be behind the mirror. This is observed in animals, and also in savages, and children, who, in order to comince themselves concerning the object seen, look and feel for it behind the mirror. The same is the case with an object lying in the water, a correct idea as to its true position, size, and form, is only gained by the touch. An idea of the distance of the object from the eye may certainly in some degree, as in the for- mer case, be formed from sight alone, so far as the distance is estimated according to the strength of the light coming from the object to the eye, but this idea, like the former, is always indefinite. A definite idea of distance, as well as of form and size, is only obtained by sight and touch, and by reflecting on the impressions made on both senses ; but for this purpose we must take into account the mus- cular motion and voluntary locomotion of the in- dividual. — Caspar Hauser,* in a detailed account of his own experience in this respect states, that upon his first liberation from confinement, whenever he looked through the window upon external objects, such as the street, garden, &c. it appeared to him as if there were a shutter quite close to his eye, and covered with confused colours of all kinds, in * Feuerbach’s Caspar Hauser — Beispiel ernes Verbrechens am Seelenleben ernes Menscken. Anspach, 1832. page 79, &c. PHYSIOLOGY OF THE EYE. 35 which he could recognise or distinguish nothing singly. He says farther, that he did not convince himself till after some time during his walks out of doors, that what had at first appeared to him as a shutter of various colours, as well as many other objects, were in reality very different things ; and that at length the shutter disappeared, and he saw and recognised all things in their just propor- tions. Persons born blind who obtain their sight by an operation in later years only, sometimes im- agine that all objects touch their eyes, and lie so near to them that they are afraid of stumbling against them ; sometimes they leap towards the moon, sup- posing that they can lay hold of it ; at other times they run after the clouds moving along the sky, in order to catch them, or commit other such extra- vagancies. A very interesting case is recorded by Cheselden,* of a person who having been born blind was successfully operated upon in the four- teenth year of his age. The case is well worthy of being read by those who take an interest in this subject. Since ideas are gained by reflection upon sensa- tion, it is further necessary in all cases, in order that an accurate idea of objects may be formed from the sense of sight, that the powers of the mind should be unimpaired, and undisturbed in * Philos. Transactions, 1728, page 447. 36 PHYSIOLOGY OF THE EYE. their exercise. A proof of this is afforded in the instance related hy Haslam,* of a boy who had no defect of sight, but was weak in understanding, and who in his seventh year was unable to esti- mate the distances of objects, especially as to height ; he would extend his hand frequently to- wards a nail on the ceiling, or towards the moon, to catch it. It is therefore the judgment which corrects and makes clear this idea, or perception of visible objects. We have hitherto considered the ideas that re- late to visible objects as being derived from visual sensation, which is produced by actual impression of an object upon the organ of sense ; but they may also, without being produced by any such impression, be called forth by the self-activity of the mind alone. For this purpose, however, it is absolutely necessary that such ideas as are derived from visual sensation should have been previously formed in the mind ; for, where visual perception, as derived from visual sensation, is wanting, i. e. where such ideas never existed, the ideas of objects which produce impressions through the sense of sight alone, are also totally wanting to the ima- gination. Thus no person who has been blind from his birth is able to form any idea of colours ; though he may form ideas about all other quali- * Haslam’s Observations on Madness and Melancholy, 2 Ed. p. 192- PHYSIOLOGY OF THE EYE. 37 ties of bodies, those of their pure visible qualities are still wanting ; neither does he ever dream of these qualities, because he has never had any perception or idea of them as derived from pure visual sensation. Ideas that lie dormant in the mind may thus be revived— -first, by the memory, either involun- tarily, as instanced in the most striking manner in dreams, in which the images of objects that have been seen before re-appear distinctly before the eye ; or voluntarily, when for instance we form at pleasure in our own mind a vivid picture of objects with which we are acquainted. This is most evidently instanced in blind persons, who were not so from their birth, but have lost their sight in later years ; they are able to represent to their minds every thing which they have formerly seen. Secondly, we can produce ideas of visible objects by the imagination. The imagination cre- ates nothing actually new, since it has always obtained beforehand through the medium of the senses the materials with which it works, which it afterwards only puts together according to its own pleasure, and arranges in new forms ad arbitrium, but in all cases agreeably to previous perception. Thus the mathematician, while engaged in the scien- tific investigation of the laws of magnitude, sketches in thought his lines and figures. Thus too the con- ceptions of the painter or of the sculptor, before they are even begun to be embodied on the canvass E 38 PHYSIOLOGY OF THE EYE. or in the stone, stand forth perfectly delineated and clothed with ideal beauty before his mental eye. This mode of producing ideas of visible ob- jects is the parent of the plastic art. Thirdly, These ideas are excited by the affections and passions. Earnest desire brings distant objects before the eye, and anxiety and fear cause phantoms or spectres to be seen. The consciousness of having been an actor in the conspiracy on the Ides of March ; disappointment as to the consequences of that action ; anticipation of an obstinate struggle in the field; apprehension as to the issue of the con- test, and the conviction that the fate of his country and of himself depended thereon : such causes were powerful enough to affect in an extraordinary manner even the manly spirit of Marcus Brutus, and to bring before his eyes the apparition of his murdered friend Caesar. This may be sufficient to explain the impression entertained by the mind of Brutus, that Caesar’s spirit was his evil genius, which would appear to him again at Philippi : for the blow struck on the Ides of March had, far contrary to his intentions, involved his country in a civil war ; and from the present position of affairs and his knowledge of the art of war, he could easily fore- see that the fate of the Roman Republic, as well as his own, must be decided in the neighbourhood of Philippi. Thus with the probable termination of the war at Philippi, became connected the deed, perpetrated before Pompev’s statue in the senate- PHYSIOLOGY OF THE EYE. 39 house, which hacl given rise to it, and the appari- tion of Csesar rose before the anxious eye of the overwhelmed Brutus. Again, under the influence of the agitation of mind, which preceded the murder of the sleeping Duncan, Macbeth exclaims : — “Is this a dagger which I see before me, The handle toward my hand ? Come, let me clutch thee : — I have thee not, and yet I see thee still. Art thou not, fatal vision, sensible To feeling, as to sight ? or art thou but A dagger of the mind a false creation, Proceeding from the heat-oppressed brain ? ” If we now turn our attention for a moment to the manner in which ideas respecting visible objects are formed from impressions made upon the sense of sight, it will be evident that their formation, or the perception of objects, depends upon a certain expertness of that sense, and that to see correctly is in fact an art. A person born blind, who has gained his sight by an operation in later years, can only acquire correct perception of the true nature and condition of visible objects by instruction, and by repeated ex- ercise of the sense of sight. He must therefore by comparing the things which present themselves to his view, and by reflecting on them learn to form for himself correct ideas concerning these objects, or in other words, he must learn to see. Just in the same manner also must every man learn to see during his childhood. But as instruction cannot be employed at the earliest period of life, it is only 40 PHYSIOLOGY OF THE EYE. by constant exercise that the child learns to sepa- rate and distinguish individual objects out of the chaos of things floating before his eyes, and to re- cognise and determine the distances, forms, and dimensions of bodies. It is observed, for example, that children, during the first few months after birth, when they wish to lay hold of their play- things, often make several ineffectual attempts be- fore they succeed. The cause of this is, that they have not yet learned to bring both eyes into harmonious bearing upon the object, and accord- ingly they see every object double ; if they now wish to lay hold of the plaything, they often ex- tend their hand, first towards the unreal object or illusion, which appears to be situated near the true object of sight. But when the child has learned by exercise to use both eyes in harmony with k each other, he learns to see singly and cor- rectly, and at the same time he is taught by ex- perience to employ in a proper manner the organ of touch and the organ of sight for the same ob- ject, and consequently is able to grasp immediately the actual object of sight. Another proof of the necessity of exercise is this. The child stretches out his hand to lay hold of the flame of a candle, however distant it may be from him, and it is only by repeated practice that he learns to estimate and determine the distance of the object accord- ing to the strength of the light coming from it to his eye, and only after some experience that he PHYSIOLOGY OF THE EYE. 41 knows whether the flame of the candle, or any other object, is within or beyond his reach. This exercise and the experience resulting from it are means by which the sense of sight is not only gradually developed and brought to perfection, but is also rendered independent of any other sense. It commences at a very early period of childhood, and the minute steps by which the sense proceeds imperceptibly towards perfection, as man acquires by degrees the power of reflection and self-con- sciousness, are entirely forgotten with all the other occurrences of early infancy, and at length in the growm-up person it has become a habit, or custom. “ Habit,” says Schiller, “ is the nurse of man,” but still it is only the nurse. Man therefore can, with no greater justice be said to bring the art of seeing, than he can be said to bring his mother- tongue, into the world with him ; he brings merely the capacity for it. Thus Voltaire* says, “ Nous apprenons a voir precisement comrae nous appre- nons a parler et a lire.” This capacity requires cultivation, which beginning in childhood, by no means ends with this period, but may be farther extended, according as circumstances, occupations, or the particular pursuits of individuals more or less favour it. As we advance in years, this cul- tivation goes on for the most part through the sense of sight alone, which has now become rela- E 2 Physique Newtonienne, Chap. vii. 42 PHYSIOLOGY OF THE EYE. tively independent ; yet there are still some occa- sions on which it is necessary that the sense of touch should come to the aid of this sense ; on the first occurrence, for instance, of objects with which we are entirely unacquainted. Now as the sense of sight in its ordinary use is exercised upon fight both in its degree and kind, and the relations of objects to space before men- tioned, viz. their distance, form, and dimensions, it is brought by particular cultivation to different degrees of refinement and perfection ; painters, for example, by the exercise of this faculty acquire a fine and delicate perception of the gradations and shades of colour, draughtsmen by the same means gain correct ideas of perspective, and military en- gineers accuracy and skill in the admeasurement of angles, distances, &c. After these inquiries with which we have hither- to been occupied, there remain still two questions to be answered, winch are of the greatest impor- tance with respect to subjective seeing. Since the image is presented in an inverted form upon the retina, as I have observed at page 22, how comes it that we nevertheless see the cause of this image, i. e. the object, in its true position, not inverted ? — However contradictory to itself this fact may appear, it yet in reality requires no ex- planation ; inasmuch as an inverted image not only of the single object, but of the ivhole field of vision and of our oivn person also, is formed upon the re- PHYSIOLOGY OP THE EYE. 43 tina. Where the whole is inverted, the whole must appear right, for the two ideas, viz. of erect- ness and inversion are only relative, and signify nothing, unless as being opposed to each other. Besides, it must be remembered that the idea in the mind is derived from sensation alone ; the mind, in perceiving a visible object, is occupied merely with forming an idea from the visual sen- sation, and does not compare the image produced on the retina by the object, with the object itself. But, it will be said, the mind may institute such a comparison by the aid of the sense of touch. In the image of a man upon the retina, for example, the head will be downwards, and the feet upwards, whereas on touching him we find the head up- wards, and the feet downwards. This apparent contradiction between the two sensations may be very simply explained, if w r e keep in mind that the idea of upwards is in point of fact of the same import as that of shy-wards, while that of down- wards is the same as earth-wards. If therefore there is in the mind the intention of touching the head of the person, which in the image upon the retina is towards the sky, and produces a corres- ponding idea ; the mind will naturally determine the organ of touch, i. e. the hand, to move itself to- wards the sky, i. e. upwards, and it will accordingly meet the head of the person. This applies equally the other way, viz. to the idea of downwards or towards the earth. 44 PHYSIOLOGY OF THE EYE. The second question is this : how comes it that with two eyes we see the object only single, and not double ? — When we view an object with one eye only, it appears in the direction of a straight line joining the object and its image on the retina, and the image is by the retina, or by a property in- herent in the sense, referred to the point where the line of visible direction meets the object. If we now direct both eyes towards the object, the two optic lines will concur at the same point of the object, and the two images of the object, viz. one to each eye, will therefore be simultaneously referred by the retina to the single point of concurrence of both optic lines ; but as it is inconsistent with the laws of nature that two things can be at the same time in the same place, it follows that the object must be seen as one and the same, or single. There exists certainly an image of the object in each eye ; but as the sensations of the two retinae, caused by the images, are, in the present case, of a corres- pondent nature, and made in the same manner and at the same time, they must harmonize with each other in respect of this triple unity of nature, manner, and time, and will therefore naturally suggest to the mind one and the same idea, and thus a single perception of the object, though de- rived from the two visual sensations, takes place. Since now it is owing to the intersection of the lines of visible direction that objects appear single when viewed with two eyes, objects situated either PHYSIOLOGY OF THE EYE. 45 before or beyond this point must of course appear double. This is a fact which may be easily proved : Fix both your eyes steadily on a part of the frame- work of a window ; any remote thing behind it and in a line with the part of the window you are looking at, for instance, the spire of a tower, or a narrow chimney, will be seen double ; if, on the contrary, you look at the remote object, the frame of the window will appear double. Again, hold two fingers at some distance and in a straight line, one behind the other, before your eyes ; if you now look at the more remote one, that which is nearer to you will appear double, and if you look at the nearer one, the remote one will appear double ; in both these cases, you will observe three fingers. To enter into an explanation of this fact would lead me too far, and does not belong to the ques- tion proposed. Physiologists have adduced a multitude of theo- ries and modes of explanation of these questions. It has been asserted (and by Gall originally) that in seeing we use only one of the eyes at a time, and never both in conjunction ; at one time the solution of the question has been found merely in the decussation of the optic nerves ( cliiasma nervo- rum opticorum ) ; at another time again habit has been assigned as affording an explanation of the difficulty. — But, to reply severally to these asser- tions ; man, being endowed with two eyes, is not a Cyclops; the operation of the mind in its 46 PHYSIOLOGY OF THE EYE. functions of perception does not admit of explana- tion by the laws which govern matter ; neither can it be said that habit is born with us. — Since sub- jective seeing in a perfect sense of sight consists in the formation of a correct idea from visual sensa- tion, that is to say, in an accurate perception of the object, these theories appear to me somewhat too partial, and not sufficiently physiological, and I think, therefore, that the present solution of the question comes nearest to the fact. CHAPTER III. IMPORTANCE AND DIGNITY OF THE EYE; AND ITS PRE-EMINENCE ABOVE THE OTHER ORGANS OF SENSE. § 1. Comparison of the sense of Sight with the other senses. It will not be difficult for us to determine what rank in the order of the senses is to be assigned to that of sight, when we have first taken a brief view of all the senses with regard to the purposes they are intended to fulfil. The sense of touch is exercised upon the me- chanical relations of bodies ; and serves for the perception of weight, form, and the position of bodies with respect to each other. The sense of taste is adapted to chemical rela- tions ; and receives impressions from fluids, or substances in the state of solution. The sense of smell is likewise adapted to chem- ical relations ; but for the perception of substances in the aeriform state. The sense of hearing is designed for the percep- tion of sound, and its modifications, tones, which are produced by the internal vibration and motion 48 IMPORTANCE AND of the particles of bodies, and which are rendered perceptible to the ear through the medium of the air. The sense of sight is adapted to light, and its modifications, colour and shade ; and, besides, to the perception of the surface, form, and position of objects, through the medium of light. The two latter senses are accordingly adapted neither to mechanical nor chemical, but only to the dynamic relations of the external world, which depend upon the mere extension of the primary cause.* * The difference of the senses depends not merely upon the peculiar mechanism of each of the organs of sense, by means of which each organ is individually adapted to those qualities of objects in the external world from which it receives impressions, but depends no less upon the peculiar kind of sensation excited in each of the proper nerves of sense, which is different in each of those nerves. Tlius the sensation of light belongs exclusively to the optic nerve, that of sound to the nerve of hearing, and so forth ; the optic nerve being no more capable of perceiving sound than the nerve of hearing is of perceiving light. This property, inherent in the nerve of each sense, and different in each, corres- ponds to the nature of the sense, and is named its energy. The excitement of this energy constitutes the sensation of the nerve, which may be different indeed in degree, but is always of the same nature ; as for instance, the differences of tone perceived by the nerve of hearing are all relations of sound — as has been al- ready shown more fully at page 31 , in treating of pure visual sensa- tion. That this peculiar property is different in each of the nerves of the senses is evident from the fact, that the same cause pro- duces a different sensation in the different senses, viz. that sen- sation which corresponds to the energy of each sense. The optic nerve, for example, perceives only the light, and the nerves of feeling perceive only the warmth, of the rays of the sun. The vibration of a tense chord is felt by the nerve of touch as a rapid DIGNITY OF THE EYE. 49 The three first-named senses, destined for mecha- nical and chemical relations, are subservient to the purposes of feeling, nutrition, and respiration, con- sequently, to animal life ; the two latter, destined for dynamic relations, render no service to the functions of animal life, but minister only to the soul. The first two or lower senses are excited to action by direct and material contact ; the two latter, or higher senses, on the contrary, by an indirect impression from a distance. The sense of smell has these points in common with the two lower senses, that it belongs to a determinate func- tion of animal life, viz. to that of respiration, and that it acts through material contact; but it ap- proaches to the two higher senses in this point, that it is capable of being affected at a distance. This sense therefore unites the inferior with the higher senses, and stands as it were between them, being connected on the one hand with the two succession of slight strokes, by the nerve of hearing it is perceived as tone, and by the optic nerve as a silent tremulous motion. Inflammation produces in the eye an appearance of light; in the ear, a sort of buzzing or singing ; and in the nerves of feeling, pain. When the eyes are placed in communication with the electric fluid, the appearance of a flash of light is occasioned in the optic nerve, in the dark ; if the ear be made the subject of the experiment, a hissing or crackling noise is produced in the nerve of hearing ; in like manner, an odour of phosphorus is produced in that of smell ; in that of taste, an alkaline or acid flavour, according to the kind of electricity ; and in the nerves of feeling, a sensation of a blow, or shock. (Volta, A. von Hum- boldt, T. Mueller, Ritter.) F 50 IMPORTANCE AND senses which are subservient to animal life, and on the other hand with the two which minister to the soul. But now if seeing be a mental touching at a distance, through the medium of the eye, and by the help of the rays of light, as we have observed at page 28, the sense of sight borders on the sense of touch, and thus a circle is completed by the series of the five senses. Hearing and sight, as the principal means by which external objects are perceived and recog- nised, are the senses employed upon the two objects which form the groundwork of all human knowledge, viz. time and space. Sound, or the internal vibration and motion of the particles of bodies, and tones, are the messen- gers which convey intelligence of the intimate nature of bodies, viz. as to their solidity and com- parative density ; just as language is the messenger which informs us of the character and inward w'orkings of the mind. The internal ear, retired within the deep recess of the bone in which it is quietly and securely lodged, hears those vibrations and motions, and hears also the language of the lips. Light discloses to our view the appearances of the material world ; and as colours, with all their variety of shade, form the garment in which these phenomena are arrayed, so is the embodied word, or written language, the garment in which the thoughts and active operations of the mind are presented to us. The eye, not retired within its DIGNITY OF THE EYE. 51 recess, but openly turned towards the external world, and endowed with the power of free motion, perceives those phenomena, and perceives the written language. The ear therefore is adapted to terrestrial objects only, for the sound which we hear belongs exclusively to the earth ; while the eye, on the contrary, is applicable to the whole system of the universe, since even the most dis- tant bodies of this system send at least an intima- tion of their existence to the eye. The former leads us, by the “ concord of sweet sounds,” to the still world of our own heart ; the latter draws our mind outwards to the contemplation of the won- drous magnificence of Nature, whose mysteries we explore by means of the eye. The ear is accord- ingly the sense for the passions and feelings, the eye the sense for the understanding. To conclude this comparison, let us turn to the Mosaic account of the creation, where we shall find it recorded, that a deep stillness and repose, and a mysterious dark- ness hovered over the chaos of things, and God commenced his work by saying, — Let there be light, — and there was light. The sublime volume of revelation declares again, that when the trumpet on the last day shall announce the judgment of the world, then, amidst the noise and tumult of the elements, shall the sun, moon, stars, and all tem- poral things perish, but the spirit of man shall enter into the bright and resplendent mansions of eternity. Sound, dependent upon the material 52 IMPORTANCE AND world, will pass away with it; the ear is conse- quently for the Finite : light, on the contrary, with which the creation of the world began, will con- tinue to exist hereafter; the eye is consequently for the Infinite. As a summary of what has been stated with re- spect to these two senses, I present the following view of the comparison : The sense of hearing is adapted to Sound Tones Matter Quality Centre Rest and Motion in Time Speech The Feelings The Finite and Temporal The sense of sight is adapted to Light Colours Form Quantity . Circumference Rest and Motion in Space Written Language The Understanding The Infinite and Eternal From the foregoing comparison of the senses with each other, we see that they are all instruments for the purpose of enabling the mind to receive impressions from the external world, and there- fore, with reference to the mode in which this is effected, the sense of touch may be called a mecha- nical sense, those of taste and smell chemical, and those of hearing and sight dynamic senses. Thus keeping in view the purposes for which they are intended, the five senses may be arranged in a progressive series, which begins with the sense of DIGNITY OF THE EYE. 53 touch as the lowest, each succeeding sense pre- senting nobler characters, till the series is ter- minated by the sense of sight. Throughout the whole range of Nature, it is observable that every created being is constituted with relation to the element in which it lives ; — the nobler the element, the nobler the creature that inhabits it. Now as light, belonging to the class of imponderable sub- stances, is a highly subtile matter, and is the pro- per element for the eye,- — for this organ is developed in, lives by, and is destined for light — the sense of sight is most justly entitled to hold the highest rank among the senses; the sense of hearing, which perceives sound through the medium of the air, which is adless subtile material, as well as the three other senses destined for gross and material substances, being certainly inferior to it. The senses are a distinguishing attribute of animal life. In man they are all susceptible of equal and simultaneous cultivation. Inferior ani- mals, on the contrary, never possess all the senses developed in equal perfection at the same time, and are therefore inferior to us in this point. In them it frequently happens that one sense enjoys a dis- tinction above the rest, according as it may be necessary to the habits or wants of a species, as for example, the sense of sight in birds. f 2 54 IMPORTANCE AND § 2. Language of the Eye. Though animals are endowed with the power of making their grosser perceptions intelligible by certain sounds to animals of the same species, yet it is not possible for them to communicate with each other in articulate tones. This incomparable distinction, the gift of speech, is granted to man alone ; he alone speaks of the various appearances of the material world, of his ideas, desires, and feelings, the recondite workings of the mind, and the sublime and eternal attributes of the Deity. Just as speech is a distinction of man from brute animals, and places him at the head of the whole animal kingdom, so also does the language of the eye claim for this organ the first place among the organs of the senses. No other sense possesses the power of indicating externally the condition and emotions of the inmost soul. The three inferior senses receive and enjoy only ; the ear too hears, but answers not ; the eye, on the contrary, receives with complacency, and replies with love. So grateful is it, that it would gladly, if possible, repay with interest every gift it receives ; the other senses, on the contrary, are mere egotists. The eye drinks in the universe, and reflects a won- drous heaven of thoughts and feelings. The language of the eye is certainly the ten- derest and the most wonderful of all languages, DIGNITY OF THE EYE. 55 inasmuch as it conveys a direct intercourse of souls with each other. It is a language which belongs to no place, yet is every where understood ; is no- where written, yet every where read ; nowhere de- termined by any fixed rules, yet every where cor- rectly spoken. It is so natural that it is as it were horn with us ; so plain, that every child, and even animals understand it ; so simple, that no one has occasion to learn it. Every one knows, speaks, and understands it. It is more eloquent, more deeply impresses the heart, and is more perfectly and quickly understood, than even the articulate accents of the lips. In the eye the soul itself ex- presses directly what the mouth seeks only to con- vey through the medium of sound and tones. The mouth is only a tedious interpreter, a circumstan- tial analyst and prolix expounder of that which the eye indicates more rapidly, more perfectly, and as sensibly as a delicate thermometer. For this reason it is, that we quite unconsciously direct our glance not to the mouth but to the eyes of the speaker, because the eye is the only portal at which souls meet, where they either lovingly em- brace, or fly repulsed from each other. When conversing even with a man who is blind, we can- not refrain from looking towards his eyes ; and al- though we find them destroyed and their light extinguished, we still feel ourselves constrained to fix our glance upon the spot from whence the soul would otherwise beam towards us. 56 IMPORTANCE AND The eyes then are true telegraphs of the soul, which 'indicate the still flame of love, the angry glow of hatred, the heaven of innocence, and the hell of vice ; and whatever moves and works within the human breast, divinely, humanly, bru- tally, or diabolically, all is distinctly expressed by the universal language of the eye. When we make any observations upon the mien of an individual, and say, such a person looks so and so, — cheerful or morose, for instance, — we mean that he allows this or that definite condition to ap- pear in his eyes — his eye expresses a cheerful or morose disposition. Men of business, when they part, wish to speak with each other again, and accordingly say : — I will speak to you to-morrow on this subject ; friends and lovers, on the contrary, think only of seeing each other again, and say : — I shall see you to-morrow, ( Au revoir — A rivederci — Auf Wiedersehen .) — Why do not lovers think equally of speaking with each other again ? Be- cause the language of words is far too poor to express the feelings they read in each other’s eyes ; because their souls wish to meet again in that heaven where they first became acquainted, and where they first welcomed the smile of dawn- ing love. Tears may be mentioned with propriety in this place, as forming a part of the language of the eyes. They are the signs of inward emotion, the expression of the highest joy or of the deepest DIGNITY OF THE^fE. 57 .4 sorrow; the salutary crisis for the relief of the feelings. § 3. Power of the glance. It is in the glance that the strength and dignity of the soul are most powerfully and vividly ex- pressed. The glance darting from the eye reaches to a considerable distance, strikes upon the minds of the beholders like a flash of lightning, and the person upon whom it falls feels himself as it were under the influence of fascination. It is an arrow which often deeply wounds ; but like the weapon with which Telephus was wounded, it has power to heal the wound it has inflicted. Wherever su- perstition has reigned, peculiar and incredible powers have been ascribed to the glance ; who has not heard, for example, of the error which pre- vailed in early times as to persons being bewitched by the glance ? and even at the present day the common people in Italy (who speak of Vocchio cattivof) and some of the Indian tribes also believe that the look has the power of producing evils and diseases of various kinds. But it is not to be de- nied, that persons endowed with superior powers of mind and firmness of character exercise by their glance a truly commanding sway over the circle which surrounds them. The glance of such per- sons strikes the orator dumb in the midst of his 58 IMPORTANCE AND harangue, arrests the enterprises of men, and checks them in their actions. By this power the hero has not unfrequently conquered his furious enemy and the opposing band of warriors. “Upon the crowd he cast a furious look, And withered all their strength." Dkyden. There are persons, moreover, whose firm glance animals regard with fear ; before which the angry mastiff cringes, the wild bull slackens his speed, and even the ferocious Hon and tiger are held in awe.* That horses are broken in by the look is a fact not unknown. * Van Aken, who possessed the art of taming wild animals, effected much in the exercise of this art by his glance. When he entered the den of the lion, he immediately arrested the eyes of the animal by a powerful and firm glance, which he kept fixed upon him, and never averted so long as he remained in the den. Those who have witnessed the performances of Van Amburgh with his various wild beasts at our theatres, may have observed that he also when in the den always fixed his eyes firmly on those of the animal with which he was more immediately occupied. After having myself closely viewed his performances several times, I had some conversation with him on the subject, when, in con- firmation of what has been already stated, he admitted that much was effected by the look in rendering wild animals subject to the will and control of man. While conversing with Van Am- burgh, I could not but notice the remarkable appearance of his eyes, which seemed to me particularly well qualified for this pur- pose. They are very large and prominent, and their glance ex- tremely keen, firm, and powerful. DIGNITY OF THE EYE. 59 § 4. The Eye in relation to the countenance. Beneath the arch of the pensive forehead, be- tween the tranquil temples and the ever watchful ears, above the cheeks where plays the smile, and the mouth whence flows the stream of eloquence, the eyes, separated by the gentle elevation of the nose, have taken up their abode. Thus even locally advanced and elevated above the rest of the senses, they are enthroned on the front and to- wards the highest part of the head, from whence they can most readily and easily command the ob- jects of their immediate neighbourhood, guide their owner on his way, and contemplate the glo- rious system of the universe. Man is therefore designed to direct his look upwards, or towards heaven. * Although the look penetrates and em- braces an immense space, the eye remains modest- ly in its recess, overshadowed by the lofty forehead and surrounded by gentle eminences, — an altar in the holy temple of thought, on which the soul offers sacrifice. Our look, when it falls upon the human countenance, glances off as it were from these eminences, and is thus conducted into the interior of the temple. It is therefore by no * The Greeks accordingly named man avdpujtroQ, (from aw, npwards, rpeiroj, to turn, and or •*. ' , i: • •% * „ v » * .; f», *t . *» ’ ’a - * » > « 1 v - • * , • • ! •> * . ? *.•* ’♦ % * . • » I- . • * * / \ •# • • . V ' * r ? K