Tr 
 
 THE ANATOMY OF THE 
 
 HUMAN EYE 
 
 AS ILLUSTRATED BY 
 ENLARGED STEREOSCOPIC PHOTOGRAPHS 
 
 BY ARTHUR THOMSON, M.A., M.B., F.R.C.S. 
 
 PROFESSOR OF HUMAN ANATOMY IN THE UNIVERSITY OF OXFORD 
 
 OXFORD 
 AT THE CLARENDON PRESS 
 
 1912 
 
- 
 
 UBI 
 
 6 
 
 CAS 
 
 HENRY FROWDE, M.A. 
 
 PUBLISHER TO THE UNIVERSITY OF OXFORD 
 
 LONDON, EDINBURGH, NEW YORK 
 
 TORONTO AND MELBOURNE 
 
PREFACE 
 
 To the Delegates of the University Press I am greatly 
 indebted for the generous assistance they have rendered in 
 the production of this work. 
 
 The Public hardly realizes how much the University does 
 through the agency of this Delegacy for the encouragement 
 of scholarship and research, since without such help much 
 unremunerative work would remain unpublished. 
 
 To Mr. W. Chesterman, my Museum Assistant, I am greatly 
 obliged for the skill and patience which he has displayed in 
 carrying out my instructions : without his co-operation it would 
 have been wellnigh impossible for me to have attained the 
 present results. 
 
 I have also to thank my Senior Demonstrator, Mr. S. E. 
 Whitnall, M.B., for his aid in revising the proof-sheets. 
 
 ARTHUR THOMSON. 
 
 OXFORD. Jan. i, 1912 
 
 285405 
 
CONTENTS 
 
 PAGE 
 
 INTRODUCTION 5 
 
 CHAPTER I 
 ANTERO-POSTERIOR SECTIONS OF THE EYE ... 7 
 
 CHAPTER II 
 DISSECTIONS OF THE EYE FROM THE FRONT . . -32 
 
 CHAPTER III 
 
 ANTERIOR HALF OF THE EYE SEEN FROM BEHIND . . 40 
 
 CHAPTER IV 
 LENS 49 
 
 CHAPTER V 
 POSTERIOR HALF OF THE EYE .... -53 
 
 KEY TO PLATES 63 
 
ERRATA 
 
 Page 42 /. 10, for 2 mm. read 3 mm. to 3-5 mm. 
 Page 54 /. 6 from foot, for No. 67 read No. 65 
 
 Thomson, Anatomy of the Human Eye 
 
 May 1912 Face p. 
 
INTRODUCTION 
 
 THE accompanying stereoscopic views of the interior of the eye 
 were prepared in illustration of a course of lectures on the gross 
 anatomy of the eye, delivered to the graduates preparing for the 
 diploma in ophthalmology of the University of Oxford. They were so 
 generally appreciated that it is hoped their publication in the present 
 form may make them accessible to those who would not otherwise 
 have an opportunity of seeing them. Many of the structures in the 
 human eye are so small that it is only possible, under ordinary circum- 
 stances, to obtain a satisfactory view of them by means of a lens of low 
 power. This usually involves their examination by monocular vision, 
 and consequently entails a loss of that stereoscopic effect which is so 
 necessary to determine their exact relations. With the object of over- 
 coming this defect, the present illustrations were prepared in such 
 a way as to preserve the stereoscopic effect, and at the same time to 
 provide for such a magnification as would render clear most of the detail 
 desired. In many instances a millimetre-scale is photographed along- 
 side the preparation, so that the student may have some approximate 
 idea of the size of the structures he is viewing. It is not suggested 
 that the present series of views should be a substitute for the ex- 
 perience gained by the actual dissection of human or other mammalian 
 eyes, but when one considers that such, more particularly human, 
 material is not easily obtainable in a sufficiently fresh condition to 
 display all the details of structure, the accompanying plates may serve 
 as a reminder of the features previously examined, and prove useful 
 as a handy means of reference when permanent preparations or museum 
 specimens are not readily accessible. 
 
 In most instances the specimens from which the photographs 
 were taken were removed within four hours after death. They were 
 hardened in a 4 % solution of formol, subsequently frozen and then 
 cut. The further dissections, where necessary, were then performed, 
 and the preparations photographed under spirit. Care was taken, as 
 far as possible, to eliminate all specimens which appeared faulty, and 
 only those which preserved the natural form and tension of the globe 
 were utilized. Every possible care was taken to avoid doubtful 
 examples, and the majority of the specimens, in so far at least as their 
 major parts are concerned, may be regarded as affording an approxi- 
 mately accurate representation of their normal condition. Doubtless 
 the more delicate structures undergo some alteration in the hardening 
 
6 '' INTRODUCTION 
 
 'process; 'but the* 'same ma)' be said of nearly all the other methods of 
 preparation that have been suggested. Opportunity was also taken 
 to secure some typical examples of foetal eyes, and photographs of 
 a few of these have been included with the object of illustrating 
 structures and relations of practical interest. 
 
 Whilst much may be learned from the dissection of a fresh eye, such 
 as that of the pig or ox, yet the student will find that even in these 
 cases a previous hardening of the specimens employed will be of 
 service in assisting him to obtain a more satisfactory view of the 
 structures involved. The brief description given in the succeeding 
 chapters lays no claim to be a complete systematic account of the 
 tissues concerned, but merely sets forth the more important details in 
 their arrangement, such as may be readily demonstrated in the sections 
 or dissections employed details which any student may verify for 
 himself by employing like or similar methods. For this reason the 
 photographs have been grouped according to the method of section 
 employed, or as illustrative of different stages in a dissection, so that 
 before proceeding to their examination the student would do well to 
 render himself familiar with the systematic account of the structure of 
 the eye given in any of the current textbooks. 
 
 The photographs have been mounted on cards of standard size, so 
 that they will fit any of the numerous stereoscopes already on the 
 market. 
 
CHAPTER I 
 
 ANTERO-POSTERIOR SECTIONS OF THE-E-YE 
 
 THIS section includes those specimens which have been divided 
 antero-posteriorly. The plane of the section may either be vertical or 
 horizontal, or possibly oblique. It is not always possible to say exactly 
 how the section was made, as in some instances no note was taken of 
 the orientation of the eye. 
 
 The preparations here reproduced, Nos. 1-18, give the student an 
 opportunity of studying the general arrangement of the parts within 
 the globe, and enable him to familiarize himself with the disposition of 
 the different layers which form its coats. Of these latter, the external 
 or sclerotic coat or sclera is seen to form about 5/6 of the circum- 
 ference of the globe. Behind, where it is pierced by the optic nerve, 
 this, the protective covering of the eye, is thickest ; here it measures 
 T mm. or a little over ; it gradually thins until it reaches the region of 
 the equator, where it averages about 0*5 mm. in thickness. Anterior to 
 this, however, it again becomes stouter owing to its fusion with the 
 tendons of insertion of the recti muscles, where it measures about 
 0-7 mm., a thickness which is maintained and increased until it reaches 
 the sclero-corneal junction, where on an average it measures 0-9 mm. in 
 thickness. 
 
 Anteriorly there is a large opening in this coat in which the cornea 
 is bedded, the cornea! aperture (foramen sclerae anterius). The edges 
 of this aperture, in the adult, are bevelled so as slightly to overlap the 
 circumference of the cornea ; the average diameter between the external 
 margins of the bevelled edge measures a little over 10 mm. (10-5 mm.), 
 whilst the width between the inner or posterior edges is about n mm. 
 
 About 3 mm. to the inner side of the vertical meridian (see 
 Nos. i, 2), and i mm. below the horizontal meridian, the sclera is pierced 
 posteriorly by the optic nerve. This, the optic foramen of the sclera 
 (foramen opticum sderae), is narrower internally, where it measures 
 
 2 mm. in diameter, than externally, where its width is a little over 
 
 3 mm. As will be seen from an inspection of the photographs (Nos. i, 
 2 > 3> 4> 5> 6, 9), the outer layers of the sclera are reflected on to the 
 dural sheath of the optic nerve, whilst the inner layer passes across 
 the narrowest part of the foramen, forming the lamina cribrosa, thus 
 appearing to pinch up the nerve as it passes through the opening. 
 Nos. i, 4, 5, 6 show very clearly how the fibres of the optic nerve 
 undergo a change at this point, for within the lamina the nerve fibres 
 
8 ANTERO-POSTERIOR SECTIONS OF THE EYE 
 
 are devoid of the medullated sheath which they acquire external to it. 
 This change in structure is indicated by the difference in colour so 
 clearly shown in the photographs. 
 
 In No. 13 the inner surface of the sclera is exposed by the complete 
 removal of the contents of the eyeball, an operation which has included 
 stripping away from the inner surface of the sclera both the nervous 
 and vascular coats. The latter the chorioid is separated from the 
 inner surface of the sclera by the perichorioidal space, through which 
 pass forward the posterior ciliary arteries and the ciliary nerves, the 
 courses of which are indicated by the lighter tracts revealed upon the 
 inner pigmented surface of the sclera, the colour of which is mainly 
 due to the remains of the lamina fusca, a finely trabecular pigmented 
 layer which bridges across the perichorioidal space. When the 
 chorioid is torn away this trabecular tissue splits into two layers, 
 one of which remains adherent to the inner surface of the sclera, as 
 has just been explained, whilst the other still clings to the outer 
 surface of the separated chorioid forming the non-vascular layer 
 which is oftentimes referred to as the lamina suprachorioidalis. The 
 anterior part of the inner surface of the sclera, which corresponds to 
 the position of the orbiculus ciliaris and the ciliary body, is much lighter 
 in colour owing to the absence of pigment : a darker zone usually indi- 
 cates the position of the ora serrata. On the inner aspect of the sclera 
 the oblique openings of the vorticose veins, commonly four in number, 
 an upper and a lower pair, can usually be seen 2 or 3 mm. behind the 
 equator, at some distance on either side of the vertical meridian. 
 
 In the foetal eyes figured (Nos. 15, 16, 17, 18), it will be seen that 
 in the newborn child the sclera constitutes 4/5 of the circumference of the 
 globe instead of 5/6 as in the adult. This, as will be shown later, is due 
 to the proportionately greater size of the cornea in the foetus. The 
 sclera does not display the variations in thickness characteristic of the 
 adult and tends to be proportionately thicker in front, where it receives 
 the cornea within the foramen sclerae anterius. Here, too, the way in 
 which the cornea is embedded differs from that already referred to in 
 the adult, for the edges of this opening are not bevelled as in the fully 
 grown eye, but rather grooved, so that there is little or no difference 
 between the measurements across the external and internal margins 
 of the aperture, the greatest width corresponding to a point inter- 
 mediate between the two margins. For further details concerning the 
 sclera see pp. 40 and 53. 
 
 The cornea in the adult forms a little more than 1/6 of the circum- 
 ference of the globe in section. In thickness the cornea averages 
 about 0-95 mm. for its central part, whilst at its periphery the radial 
 diameter is increased to 1-19 mm. It measures from 10-5 to n mm. from 
 side to side, and is bedded within the foramen sclerae anterius in such 
 
ANTERO-POSTERIOR SECTIONS OF THE EYE 9 
 
 a way that the bevelled edge of that aperture overlaps it slightly 
 around its circumference, where the tissues of the sclera and cornea 
 are blended. 
 
 As a result of the differences in the lengths of the radii of the circles 
 of which the cornea and sclera form arcs, the external corneal surface 
 projects beyond a chord passing through its circumference, .where it 
 unites with the sclera externally (sulcus sclerae externus) to the extent 
 on an average of 2-5 mm., ranging from 2-2 to 3-2 in the specimens 
 examined. 
 
 Owing to the bevel of the sides of the foramen sclerae anterius, the 
 area of the cornea, when viewed from within, is about i mm. wider in 
 its diameter than that exposed externally. 
 
 The inner surface of the cornea not only forms part of the arc of 
 a smaller circle than that of the external surface, but the centres of the 
 two circles do not coincide, that of the smaller circle lying anterior to 
 the centre of the larger circle by a distance equal to that of the central 
 thickness of the cornea. The measures taken from the specimens 
 examined yield an average radial length for the curve of the external 
 surface of 8-4 mm., ranging from 10 mm. to 8 mm., whilst for the inner 
 surface the radius of the curve averages 6-8 mm., ranging from 9 mm. 
 to 6 mm. 
 
 In this way the increased thickness of the cornea at its periphery is 
 accounted for, but some arrangement is necessary whereby the thicker 
 corneal margin may accommodate itself to the bevelled edge of the 
 corneal aperture of the sclera. This is provided for by the rounding 
 off of the inner corneal margin, where it becomes confluent with the 
 inner surface of the scleral margin, so that in place of forming with the 
 latter a uniform flowing curve, it makes, by the abruptness of its over- 
 hang, a sulcus, or groove, at the point where it becomes blended with 
 the scleral tissue. This can be well seen in Nos. 4, n. It is here, in 
 the neighbourhood of the filtration angle, that the groove so formed lies, 
 to which the name sulcus circularis corneae has been applied. The 
 further consideration of this arrangement is postponed until the gross 
 anatomy of the filtration angle is considered (see p. 15) ; meanwhile, it 
 may be sufficient to note that the presence of this groove is again clearly 
 demonstrated in Nos. 12 (d) and 13 (b\ where in the former the iris 
 has been removed, whilst in the latter the whole of the uveal tract has 
 been stripped off from the inner surface of the sclera. A further view 
 of the sulcus is also obtained in No. 47, where the inner surfaces of the 
 cornea and sclera are displayed. 
 
 In the full-time foetus (No. 15), the cornea amounts to about 1/5 of the 
 circumference of the globe on section ; its transverse diameter measures 
 about 10-6 mm. in the specimens examined, so that there is comparatively 
 little increase in its growth requisite to reach the adult proportions. It 
 
io ANTERO-POSTERIOR SECTIONS OF THE EYE 
 
 follows, then, that the increase in the size of the globe after birth is 
 mainly due to the expansion of the scleral part of the eyeball and its 
 contents. At birth the thickness of the cornea is not only propor- 
 tionately, but also absolutely greater than the thickness of the cornea 
 in the adult. In the full-time foetus it measures 1-40 mm. at the centre, 
 and increases to 1-60 mm. at the periphery. In a 6^-months' foetus 
 the corresponding measurements were 1-30 mm. and 1-40 mm. respec- 
 tively. The manner in which the cornea is bedded in the sclera within 
 the foramen sclerae anterius also differs from that which is characteristic 
 of the adult: whereas in the latter the cornea is set within the bevelled 
 edge of the sclera, it appears in the foetus to be sunk in a groove 
 within the scleral substance, the edges of which overlap it to a slight 
 extent both in front and behind. For further details concerning the 
 cornea see p. 41. 
 
 The uveal tract or vascular coat. This comprises the chorioid, 
 the ciliary body, and the iris, and constitutes the middle coat of the 
 eyeball. 
 
 The chorioid (choroid). This vascular layer clothes the inner sur- 
 face of the sclera as far forward as the ora serrata, the scalloped edge 
 of the nervous layer of the retina. In front of this the chorioid is con- 
 tinuous with the ciliary body, a structure which reaches anteriorly to near 
 the internal sclero-corneal junction, at which point it becomes continuous 
 with the curtain of the aqueous chamber, the iris. The inner surface 
 of the ciliary body anterior to the ora serrata exhibits a smooth, striated 
 appearance, the orbiculus ciliaris, which is replaced in front by numerous 
 folded processes, the ciliary processes, the rounded anterior extremities 
 of which project behind the iris and are directed inwards towards the 
 circumference of the lens, from which they are separated by an interval 
 (the circumlental space) measuring on an average about i mm. across. 
 
 As has been said, the outline of the ora serrata marks the anterior 
 limit of the chorioid proper. The position of this edge varies consider- 
 ably in different eyes and in different parts of its circumference. From 
 measurements taken on my own specimens I find that the ora serrata lies 
 on an average about 6-2 mm. behind the external sclero-corneal junction 
 (sulcus sclerae externus) . 
 
 As the chorioid lies within the sclera it is separated from it by the 
 perichorioidal lymph space, a space which, as already described, is 
 seen to be broken up by the trabecular tissue of the lamina fusca, 
 which unites the chorioid to the sclera. Owing to rough handling 
 or inequalities in the hardening process, the chorioid has a tendency to 
 separate from the inner surface of the sclera, in which case the lamina 
 fusca is either stretched or torn into two layers, the outer of which 
 adheres to the sclera and imparts to it its brown pigmented appear- 
 ance, whilst the inner still remains attached to the vascular chorioid, 
 
ANTERO-POSTERIOR SECTIONS OF THE EYE n 
 
 constituting what is often described as the peri- or siiprachorioidal 
 membrane, the presence of which gives the fluffy appearance to the 
 outer surface of the separated chorioid. 
 
 These appearances may be seen in some of the photographs (Nos. 7, 
 8, 10, 12, 15), where a partial separation of the chorioid from the sclera 
 reveals in some instances the finely stretched open tissue olthe lamina 
 fusca. In the region around the optic nerve the adherence of the 
 chorioid to the sclera is more intimate, owing to the passage of the 
 short posterior ciliary arteries from one coat to the other. A short 
 distance behind the equator the emergence of the four or five great 
 vorticose veins at more or less regular intervals apart, on their way to 
 pierce the sclera, serves to link together the chorioidal and scleral coats 
 more intimately. The inner layer of the chorioid is formed of con- 
 densed connective tissue called the lamina basalis or lamina vitrea. 
 This lies in contact internally with the pigment layer of the retina, and 
 so intimate is the connexion that if an attempt be made to separate 
 the retina from the chorioid the pigment layer of the retina almost 
 invariably remains adherent to the inner surface of the chorioid, a cir- 
 cumstance which explains why that pigmented layer was formerly 
 regarded as one of the constituents of the middle coat, before its true 
 significance was revealed by a knowledge of its development. It is 
 a matter of great difficulty in the preparation of eyes for demonstration 
 purposes to preserve intact the union of these several layers, and in the 
 photographs there are numerous examples (Nos. 3, 4, 5, 6, 10, &c.) in 
 which the retina is separated from the chorioid ; but note that in every 
 case the separated retina, comprising its nervous elements, appears 
 white, owing to the fact that its pigment layer still remains united to 
 the chorioid, the line of cleavage through the retina corresponding 
 to the cleft which in early development separates the outer from the 
 inner layer of the secondary optic vesicle. 
 
 Between the lamina basalis internally and the lamina suprachorioidea 
 externally, the structure of the chorioid consists of a connective-tissue 
 stroma, containing many blood-vessels and a considerable amount of 
 pigment. As this region derives its blood supply from the short 
 posterior ciliary arteries, it follows that the chorioid is thicker behind 
 than in front, the thickness ranging from o-i mm. in the region around 
 the entrance of the optic nerve to 0-06 mm. in the neighbourhood of the 
 ora serrata. Within its substance the vessels of the chorioid are so 
 arranged that the larger vessels form an external layer, the lamina 
 vasculosa, whilst a thinner internal layer, made up of fine capillaries, 
 constitutes the chorio-capillaris. Distributed most externally in the 
 lamina vasculosa are the whorl-like groups of the tributaries of the 
 vorticose veins, an arrangement which is readily displayed, as in photo- 
 graph No. 65, where the chorioid has been stripped away from the 
 
12 ANTERO-POSTERIOR SECTIONS OF THE EYE 
 
 sclera so as to expose its outer surface. In Nos. n and 12 the inner 
 or retinal surface of the chorioid is exposed by the removal of the 
 nervous layers of the retina ; here the pigmented retinal layer is still in 
 most part in contact with the chorioid. The lighter tracts which are 
 seen on the surface of the chorioid correspond to areas where the pig- 
 ment layer has to a greater extent been removed owing to its more 
 intimate adherence to the nervous layers of the retina, which in corre- 
 sponding situations were thrown into folds, produced either by the 
 irregular contraction of that membrane under the influence of hardening 
 agents, or by post-mortem changes. 
 
 In the full-time foetal eye exhibited in No. 5, the chorioid is 
 characterized by a greater proportionate thickness, and is also remark- 
 able in that its anterior limit, determined by the position of the ora 
 serrata, is placed much further forward than in the adult. For further 
 details concerning the chorioid see pp. 41 and 54. 
 
 In front of the ora serrata the middle coat or uveal tract of the eye 
 extends forwards to reach the region of the sclero-corneal junction, from 
 which it passes inwards to form the iris. 
 
 The ciliary body is that part of it which stretches from the ora ser- 
 rata to the internal sclero-corneal junction. The inner surface of this 
 area is deeply pigmented, and is divisible into two parts. The posterior, 
 called the orbiculus ciliaris, lies immediately in front of the ora serrata, 
 and forms a zone measuring on an average 3-6 mm. from before back- 
 wards, with a range between 4 mm. and 3-5 mm. in individual cases. 
 This zone presents a smooth deeply pigmented appearance, displaying 
 a radial striation due to the arrangement of the vessels which lie within 
 its substance, for here the chorioid, with which it is continuous poste- 
 riorly, loses its chorio-capillary layer, and the vessels of the vascular 
 lamina, rearranging themselves in parallel bundles which are connected 
 in front with the ciliary processes, give rise to the striation aforemen- 
 tioned. The other constituents of the chorioid here persist, the inner 
 basal membrane being continued forward, with the pigment layer of the 
 retina overlying it and closely adherent to its inner surface. 
 
 Be it remembered that the nervous layer of the retina does not 
 extend in front of the ora serrata. 
 
 The anterior part of the inner surface of the ciliary body is marked 
 by a series of alternating ridges and furrows like the folds of a ruff. 
 These together constitute the corona radiata, or corona ciliaris, which is 
 made up of from 67 to 84 ciliary processes, the average number being 
 about 76 or 77. 
 
 The anterior extremities of these ciliary processes are club-shaped, and 
 project inwards, behind the iris, towards the circumference of the lens, 
 from which they are separated by a variable interval, the circiimlental 
 space, which measures on an average i mm. On meridional section 
 
ANTERO-POSTERIOR SECTIONS OF THE EYE 13 
 
 these processes appear pyriform in shape, their external surface being 
 directed towards the inner surface of the sclera, from which, however, 
 they are separated by the ciliary muscle, another important constituent 
 of the ciliary body. The ciliary processes are unequal in their disposi- 
 tion ; their length from the point where they arise from the orbiculus to 
 their blunt rounded extremity, measures on an average 3 to 3>5-tnm., but 
 they are not all the same size, and not unfrequently the corona displays 
 an arrangement in which the large and small processes appear to alter- 
 nate with each other. Not uncommonly, these deeply pigmented folds 
 exhibit a lighter appearance along their edges, just as if some of the 
 pigment had been rubbed off. 
 
 Lying to the outer side of the ciliary processes, and constituting 
 quite half the thickness of the ciliary body, is the ciliary muscle. This 
 consists of a zone of smooth muscle divided into two parts. The 
 external portion, the fibrae meridionales of Brucke, is wedge-shaped; 
 the edge of the wedge corresponds to the attachment of the muscle 
 to the annular ligament at the internal sclero-corneal junction ; from 
 this point its fibres pass backwards in a meridional direction, to be lost 
 in the substance of the ciliary processes and the outer surface of the orbi- 
 culus. The external surface of this part of the muscle is exposed when 
 the ciliary body is torn away from the inner surface of the sclera, and 
 differs from the rest of the uveal tract by its lighter grey colour, as may 
 be seen in photographs Nos. 20, 26 and 65. Lying to the inner side of 
 the summit of the wedge formed by the above-mentioned fibres, and cor- 
 responding to the bases of the free projecting extremities of the ciliary 
 processes, as well as to the attachment of the periphery of the iris, 
 is a group of fibres of varying degrees of thickness arranged circum- 
 ferentially ; these constitute the circular fibres of Muller. For further 
 details concerning the ciliary body see pp. 36 and 42. 
 
 Overlying the inner surface of the ciliary process are seen certain 
 delicate layers which are intimately connected with them. These layers, 
 which separate towards the anterior extremity of the ciliary processes 
 into two more or less distinct laminae, bridge across the interval between 
 the ends of the ciliary processes and the circumference of the lens, and 
 form the zonule of Zinn, or the suspensory apparatus of the lens. They 
 will be described in greater detail hereafter (p. 37) ; meanwhile they are 
 mentioned now because they are well seen in photographs Nos. 8 and 9, 
 in which it clearly appears that they form a partition which separates 
 the aqueous chamber in front from the vitreous behind. 
 
 In the same photographs the so-called canal of Petit is displayed as 
 the interval, shown in section, which surrounds the circumference of the 
 lens between the anterior and posterior fibres of the zonule of Zinn. 
 
 The iris (Nos. i, 2, 3, 4, 8 and 10), in a meridional section of the eye, 
 appears like a diaphragm, measuring on an average n mm. in diameter, 
 
i 4 ANTERO-POSTERIOR SECTIONS OF THE EYE 
 
 placed within the aqueous chamber. By its circumference it is continuous 
 with the rest of the uveal tract, and blends with the tissue immediately 
 in front of the fore part of the blunt extremities of the ciliary processes, 
 and immediately to the inner side of the summit of the wedge-shaped 
 mass of the ciliary muscle, the circular fibres of which lie just external 
 to, and behind, its attachment. 
 
 Note that this attachment is the thinnest part of the iris. I find its 
 average thickness in the specimens at my disposal is 0-2 mm. ; it tends 
 to become thinner when the iris is stretched during contraction of the 
 pupil, and is thicker when the pupil is dilated. Further, it should be 
 observed that this, the attached edge of the iris, is turned slightly back- 
 wards to blend with the fore parts of the ciliary processes, so that the 
 interval between these two structures, or what corresponds to the 
 lateral extension of the posterior camera of the aqueous chamber, displays 
 in section the appearance of curving round the extremities of the 
 ciliary processes. This will of course be subject to modification accord- 
 ing to the tension of the iris. 
 
 In most instances the section has passed through the pupil, the 
 width of which will vary according to its state of contraction. The 
 circumference of the pupil is bevelled at the expense of its anterior 
 margin, so that it displays a chisel-shaped edge on section. The thin 
 margin, however, is not sharp and clean cut, but is finely crenated owing 
 to the disposition of the minute folds which are arranged radially on the 
 posterior surface of the iris close to the pupillary edge. The body 
 of the iris will vary in thickness according to its state of contraction. 
 With a widely dilated pupil it may measure 0-75 in thickness, whilst 
 with a contracted pupil it may be reduced to 0-3 mm. The posterior 
 surface usually displays an evenly flowing outline, whilst the anterior 
 surface exhibits a series of folds and depressions, particularly when the 
 pupil is dilated. 
 
 The relation of the iris to the aqueous chamber can now be studied. 
 It serves as a partition which subdivides that cavity into two chambers, 
 an anterior and posterior, which lie respectively in front of and behind 
 the iris, and which communicate freely with each other through the 
 pupillary aperture. 
 
 The anterior chamber, bounded in front by the concave inner sur- 
 face of the cornea, is limited behind by the anterior surface of the iris. 
 Laterally, these two walls meet in the region of the internal sclero-corneal 
 junction, where they form what is known as the iridial or filtration angle. 
 Centrally, the posterior wall of the anterior chamber corresponds to that 
 portion of the anterior surface of the lens which is exposed through the 
 pupil. The depth of the anterior chamber, i.e. the measurement from 
 the posterior surface of the central part of the cornea to the anterior 
 surface of the lens, exposed through the pupil, varies in the same 
 
ANTERO-POSTERIOR SECTIONS OF THE EYE 15 
 
 individual according to the varying degree of convexity of the anterior 
 surface of the lens in different states of accommodation. Age also 
 affects its depth : it is stated to be deeper in the young and to become 
 shallower with advancing years. In myopic eyes its antero-posterior 
 diameter is greater than in the hyperopic. In the specimens examined 
 the depth of the anterior chamber ranges from 2 mm. to 3 mm., yielding 
 an average of 2-2 mm. 
 
 The posterior chamber corresponds to that part of the cavity of the 
 aqueous chamber which lies between the iris in front and the anterior 
 surface of the lens lateral to the pupil, the zonula ciliaris, and the 
 anterior rounded extremities of the ciliary processes and the recesses 
 between them behind. At, and for some little distance from, the 
 pupillary margin the posterior surface of the iris lies in contact with 
 the anterior surface of the lens, over which it can glide freely. It 
 passes from the lens, however, in a tangential fashion so as to stretch 
 across the interval which separates the lens from the ciliary processes, 
 in front of and on a plane anterior to the anterior lamina of the zonula 
 ciliaris, and some little distance in front of the rounded extremities of 
 the ciliary processes, around which it gently curves towards its circum- 
 ferential limit. In front, the posterior chamber communicates with the 
 anterior chamber through the pupil, whilst posteriorly it is separated 
 only by the zonula ciliaris or zonule of Zinn from the vitreous chamber, 
 as may be seen in many of the photographs of the succeeding series, 
 Nos. 27, 31, 39 and 40. 
 
 In the foetus at birth (No. 15) the anterior chamber is shallow, 
 owing to the greater convexity of the anterior surface of the lens ; and 
 in the posterior chamber, the part of the posterior wall formed by the 
 zonula ciliaris is represented in deep shadow. In this specimen the 
 width between the fore part of the ciliary process and the equator of 
 the lens measures 0-5 mm. 
 
 In the eye of the 6|-months' foetus (No. 16) the aqueous chamber, 
 including under that name the space between the cornea and lens, is 
 only about 0-5 mm. in depth. As will be seen, this is subdivided by the 
 pupillary membrane, which arises from the anterior surface of the iris 
 a little wide of the pupillary margin, and stretches across that aperture 
 so as to completely divide the anterior from the posterior camera of the 
 aqueous chamber. What corresponds to the anterior chamber in the 
 adult, i.e. that part of the aqueous chamber which lies between the iris 
 and the cornea, is at this stage reduced to the proportions of a linear 
 cleft. For further details concerning the iris see pp. 32 and 43. 
 
 The region around the Filtration Angle. 
 
 The iridial or filtration angle coincides in position with the circum- 
 ference of the cavity of the anterior chamber, and corresponds to the 
 
16 ANTERO-POSTERIOR SECTIONS OF THE EYE 
 
 cleft between the iris and the internal sclero-corneal junction. Here 
 a number of important structures demand attention. 
 
 Good views of this region are displayed in Nos. i, 2, 3, 4, 5, 8 and 10 ; 
 but it will be noticed that the appearance in all of these photographs 
 does not correspond. It will be observed that these differences bear 
 some relation to the state of contraction of the iris, for in No. i, where 
 the specimen exhibits a small pupil with a thin and stretched iris, the 
 form of the iridial angle is not the same as that shown in the photo- 
 graphs Nos. 3, 4, 5, 8 and 10, in which the pupils are more widely dilated 
 and the iris thickened owing to its radial contraction. 
 
 Taking a specimen with a pupil of intermediate size, such as that 
 seen in No. 4, it will be observed that at the internal sclero-corneal 
 junction the cornea is thicker than the sclera ; in order that the two 
 edges may be brought into harmony the postero-internal margin of the 
 cornea is rounded off so as to form a projecting shoulder, which over- 
 hangs the sloping surface of the sclera with which it unites : this is well 
 seen on the left side of the photograph. The result of this arrange- 
 ment is that a recess or groove is formed immediately behind the 
 sclero-corneal junction which corresponds with the extreme periphery 
 of the anterior chamber. When describing the manner in which the 
 ciliary border of the iris was attached to the ciliary body, attention 
 was drawn to the fact that the attached edge of the iris was turned 
 somewhat backwards. Consequently, as may be seen in Nos. 4, 8 and 
 10, when through contraction of its radial fibres the iris is thickened its 
 outer circumference forms a bevelled edge, in front of its attached 
 margin, which fits into the groove in the outer wall of the angle 
 immediately behind the internal sclero-corneal junction, the fore part 
 of the groove corresponding to the overhanging shoulder of the cornea, 
 the outer wall being formed by the slope of the sclera immediately 
 behind the internal sclero-corneal junction. In this way a recess is 
 provided wherein the thickened margin of the iris can be withdrawn, 
 without, however, necessitating the obliteration of the space between 
 the opposing surfaces. The deepest part of the intervening recess is 
 thus left open for the free circulation of fluids. A better view of this 
 groove, which for convenience may be called the sulcus circularis 
 corneae, can be obtained by tearing the iris away from its ciliary attach- 
 ment; this is shown in No. 12, where the groove is displayed as a 
 double contour lying in front of the linear area from which the iris has 
 been detached. Further dissections of the same features are represented 
 in Nos. 12 and 47, and in No. 14 the groove is further demonstrated 
 by the expedient of pulling back the iris after the lens has been re- 
 moved. But the bottom of the recess between the iridial attachment 
 and the inner surface of the sclera is not so clean-cut as might be 
 supposed. Curving round the bottom of this, from the iris on the inner 
 
FIG. i. ENLARGED GENERAL VIEW OF THE IRIDIAL ANGLE. 
 
 Canal of Schlemm. 
 
 Trabecular tissue of pectinate ligament. 
 Scleral vein. 
 Dense scleral tissue. 
 
 Scleral process or spur projecting inwards and forwards 
 from the sclera close behind the canal of Schlemm ; 
 this corresponds to the annular ligament in section. 
 Radial muscular fibres of the iris extending outwards 
 
 below the iridial angle. 
 Iridial angle. 
 
 Meridional fibres of the ciliary muscle. 
 /". Circular fibres of the ciliary muscle. 
 
 The microphotograph has been slightly touched up so as to emphasize the 
 differentiation of tissue which is revealed by the Malory stain. 
 
 / 
 
 f: 
 
 To face p. 17 
 
ANTERO-POSTER10R SECTIONS OF THE EYE 17 
 
 side to the sloping surface of the sclera just behind the internal sclero- 
 corneal junction, is a small amount of lax trabecular tissue, the surface 
 of which, directed to the anterior chamber, is overlain by an endothelial 
 covering continuous in front with the endothelial layer lining the 
 inner surface of the posterior limiting membrane of the cornea (Descemet's 
 membrane), and confluent behind with the anterior endotheliaL layer 
 of the iris. This, together with the lax trabecular tissue beneath 
 formed by the splitting up of Descemet's membrane, is the feeble 
 representative in man of the much more extensively developed 
 structure seen in mammals other than the Primates, called the pectinate 
 ligament. The laxity and elasticity of this tissue can easily be demon- 
 strated in a recent specimen by gently pulling on the iris, under which 
 conditions the groove, as such, tends to be obliterated, so simulating 
 the appearance displayed in photographs Nos. i and 2, where the 
 iridial angle now exhibits an appearance more closely resembling the 
 figures of it presented in the various textbooks. In these specimens 
 (Nos. i and 2) the pupil is contracted and the iris is thinned and much 
 stretched ; under these conditions the traction exercised through its 
 attached margin pulls out the lax tissue which forms the floor and 
 outer wall of the iridial angle, and so leads to the more or less 
 complete obliteration of the groove so well displayed in the other 
 photographs (Nos. 3, 4, 8 and lo). 1 A more detailed examination of this 
 region under a higher degree of magnification will enable the student 
 to realize the general arrangement of the parts around the iridial angle. 
 Fig. i is a photomicrographic view of the appearances displayed. 
 The upper edge of the figure passes through the cornea and sclera 
 at the level of the internal sclero-corneal junction. The iridial or 
 filtration angle (g) lies between the periphery or ciliary attachment of the 
 iris internally and the sclera (d), with its associated structures externally. 
 The dense scleral tissue (d) traversed, as may be seen in the section, by 
 a scleral vein (c), lies to the outer side of an elongated cleft (a) the canal 
 of Schlemm the outer wall of which it forms. Posterior to the canal 
 of Schlemm a wedge-shaped process of scleral tissue (e) is seen pro- 
 jecting inwards and forwards from the substance of the outer coat. 
 This represents the appearance displayed by the annular ligament on 
 section, and has been named the scleral process or spur (calcar sclerae). 
 Lying in front of this and to the inner side of the canal of Schlemm 
 (a) is the trabecular tissue of t\\e pectinate ligament (b): this consists of 
 an open meshwork of fibre-elastic tissue, continuous in front with 
 Descemet's membrane, which lines the inner surface of the cornea. 
 Posteriorly, the majority of the fibres of the pectinate ligament are 
 
 1 For a fuller account of this region see a paper ' On the Gross Anatomy of the 
 Filtration Angle of the Human Eye', A. Thomson, The Ophthalmoscope, September, 
 1910, and July, 1911. 
 
i8 ANTERO-POSTERIOR SECTIONS OF THE EYE 
 
 seen to be attached to the front of the scleral process (e); a few of 
 them, however, pass backwards over the summit of the scleral process 
 and blend with the connective tissue which surrounds the bottom of 
 the iridial angle (g), becoming continuous internally with the stroma 
 of the iris. Behind the scleral process (e) and closely applied to the 
 inner surface of the sclera (d), are the meridional fibres of the ciliary 
 muscle (h) ; these, be it noted, do not pass in front or over the summit 
 of the scleral process (e). To the inner side of the meridional fibres lie 
 the circular fibres of the ciliary muscle (/), and to the mass of these, as 
 shown in section, may be traced a few of the scattered radial fibres of 
 the dilator pupillae (/). 
 
 The canal of Schlemm (d) is revealed as an empty, open, endothelial- 
 lined cleft, having its outer wall formed by dense scleral tissue (d), whilst 
 its inner wall is made up of the trabecular tissue of the pectinate liga- 
 ment (k}. As the canal lies in this position its hinder part occupies the 
 angular recess formed by the inward and forward projection of the 
 scleral process (e). The trabecular tissue of the pectinate ligament, as 
 it lies to the inner side of Schlemm's canal, is traversed by many narrow 
 channels, which are lined by an extension of the endothelial layer 
 which overlies Descemet's membrane, and afford a passage-way for 
 fluids from the anterior chamber into the canal of Schlemm. The 
 canal of Schlemm is therefore a channel or series of channels possessing 
 more or less rigid external walls, due to the density of the scleral tissue 
 which here invests it ; whilst its inner wall, formed as it is by the open 
 trabecular tissue of the pectinate ligament, will be subject to such 
 changes as may be induced by the stretching of that tissue. 
 
 It has been suggested 1 that the scleral process (e) is not a fixed point, 
 but responds to the influence of the combined contraction of the ciliary 
 muscle and the sphincter of the pupil, moving backwards and inwards, 
 thereby stretching the pectinate ligament and opening up the iridial 
 angle, at the same time that it pulls inwards the inner wall of the canal 
 of Schlemm, so increasing its lumen and thereby establishing a condition 
 of negative pressure within it. When the muscles cease to contract 
 the scleral process is pulled forward again by the elasticity of the 
 pectinate ligament, the lumen of the canal is reduced, and a gentle pres- 
 sure is exercised on its contents so as to force them onwards into the 
 surrounding circulation. For the evidence on which this suggestion is 
 based see the article already cited. 
 
 The Retina, or nervous tunic. The reader may be reminded that 
 this layer is formed by the invagination of the wall of the primary optic 
 vesicle to form the optic cup. The two walls of which the cup is 
 formed are originally separated by the cavity of the optic vesicle, 
 
 1 Ophthalmoscope, vol. ix, July, 1911, 'The Filtration Angle, &c.'; A. Thomson, 
 p. 470. 
 
ANTERO-POSTERIOR SECTIONS OF THE EYE 19 
 
 a space which at an early stage of development is continuous with the 
 ventricular cavity of the brain. This double-walled optic cup, of 
 which the inturned edge corresponds in the adult to the circumference 
 of the pupil, comes to have developed around it the uveal tract or 
 vascular coat. The outer wall of the optic cup is therefore closely 
 applied everywhere to the inner surface of the uveal tract,r viz. to the 
 chorioid, the orbiculus ciliaris, the ciliary processes, and the iris. To 
 the inner side of the outer wall of the optic cup lies the inner wall of 
 the cup, separated at first by the remains of the cavity of the optic 
 vesicle a space which in the adult is represented by the intervals 
 between the rods and cones and the processes extending from the 
 pigment cells. There seems good reason for believing that these 
 intervals constitute a lymph space between the two layers. Now the 
 two walls of the cup undergo remarkable changes in the process of 
 development. The whole of the outer wall becomes converted into 
 a thin pigmented layer, the pigment layer of the retina. This, as has 
 been stated, is applied to the inner surface of the uveal tract, and so 
 intimate is the union that in dissecting the coats of the eye it generally 
 adheres to the vascular tunic, thus accounting for the view which was 
 formerly held that it was to be regarded as one of the constituents of 
 the uveal or chorioid layer. Its separation from the inner wall of the 
 optic cup takes place along the line of the cavity of the primitive optic 
 vesicle, where the union of the two layers appears to be weaker than 
 the connexion between the pigment layer of the retina and the inner 
 surface of the uveal tract. 
 
 The inner wall of the optic cup, which is everywhere applied to the 
 inner surface of the outer wall or pigmented layer, undergoes in the 
 process of development changes which vary in accordance with 
 the position which it occupies. From the optic nerve as far forwards 
 as the ora serrata, the inner wall of the cup forms the nervous layer or 
 pars optica retinae. In contrast with this relatively thick stratum, the 
 inner wall of the optic cup in front of the ora serrata becomes reduced 
 to the thickness of a single cellular layer, which, now more firmly 
 adherent to the pigment layer, overlies the inner surface of that struc- 
 ture, and is continued onwards over the orbiculus ciliaris, the ciliary 
 processes, and the posterior surface of the iris until the two layers, viz. 
 those developed from the inner and outer walls of the optic cup, become 
 continuous with each other at the circumference of the pupillary aperture. 
 
 According as this stratum, developed from the inner wall of the optic 
 cup, overlies the orbiculus and ciliary processes, it is spoken of as the 
 pars ciliaris retinae, whilst where it is applied to the posterior surface of 
 the iris it is referred to as the pars iridica retinae. 
 
 A consideration of the foregoing details will enable the student to 
 realize the complexity of the layer which is now being considered, and 
 
 B 2 
 
20 ANTERO-POSTERIOR SECTIONS OF THE EYE 
 
 will account for the apparent discrepancies which the dissections reveal 
 when we attempt to examine the retina as one organic layer. The 
 facility with which the pars optica retinae separates from the external or 
 pigmented layer is one of the difficulties which the preparateur has 
 constantly to endeavour to overcome in the making of large sections, 
 and it is only in exceptional cases, due partly to the efficiency of the 
 hardening reagent, and also to the avoidance of post-mortem change, 
 that satisfactory results can be obtained. 
 
 Owing to the changes which take place after death, and the influence 
 of the hardening reagents employed, the pars optica retinae loses its 
 normal transparency and acquires a mat -white semi-translucent appear- 
 ance ; further, in place of being evenly spread over the surface of the 
 chorioid, it tends to become creased and wrinkled in a meridional direc- 
 tion. These appearances are well seen in Nos. i, 2, 3, 4, 8 and 10. In 
 some of the specimens more or less extensive separation has taken 
 place between the internal nervous layer and the pigmented lamina of 
 the retina. Nos. i and 2 are the photographs which exhibit it with least 
 disturbance of the parts. In the other photographs, where separation 
 has occurred between the two layers, it will be noticed that by the 
 inturning of the cut edge the outer surface of the nervous layer is often 
 exposed, and this, it will be observed, is free from pigment, the pig- 
 mented layer to which it was applied being retained in situ in contact 
 with the inner surface of the chorioid. 
 
 Proceeding now to examine the pars optica retinae as displayed in 
 meridional sections of the eye, it will be seen to form the inner lining 
 of the wall of the eyeball as far forwards as the ora serrata, which as 
 a rule is situated about 6 mm. (6-2, see also p. 10) behind the external 
 sclero-corneal junction. 
 
 According to whether the meridional section has been made in the 
 horizontal or vertical plane, a difference is to be noted in the relative 
 position of the passage of the optic nerve through the scleral coat. 
 Photographs Nos. i and 2 exhibit this appearance when the section is 
 carried horizontally through the optic nerve ; here the nerve is seen to 
 pierce the sclerotic 3 mm. to one or other side of the posterior pole of the 
 eye. In consequence of this arrangement, the one side of the pars 
 optica retinae, as seen in section, is shorter than the other. The shorter 
 side is always that which corresponds to the nasal surface of the globe, 
 whilst the longer side lines the inner surface of the temporal aspect of 
 the eyeball. When the meridional section is made in a vertical plane 
 passing through the optic nerve, the point of entrance of the nerve 
 corresponds more closely to the posterior pole, being situated only 
 about i mm. below it; consequently there is only a slight difference 
 in the extent of surface covered by the upper and lower parts of the 
 retina. This is well displayed in Nos. 3, 4, 5, 6 and 9. 
 
ANTEROPOSTERIOR SECTIONS OF THE EYE 21 
 
 The appearance of the retina exhibited in the various specimens 
 photographed (Nos. i, 2, 3, 4, 5, 6, 9 and 10) varies considerably. In some 
 (Nos. i and 2), owing to a greater degree of transparency in the hardened 
 retina, the vessels of that layer are fairly well displayed ; whilst in the 
 others, due doubtless to the difference in the action of the hardening 
 reagent in conjunction with the post-mortem changes in the specimen at 
 the time it was received, the retina is seen to be more opaque, and con- 
 sequently the course of the vessels is not so well displayed. For the 
 same reasons the evenness with which the pars optica retinae is spread 
 over the inner surface of the chorioid varies in the different specimens. 
 In Nos. i and 2 there has been the least disturbance of the layers ; here, 
 along the edges of the section, the retina is shown but little displaced, 
 the only appearance of the surface of the retina which we may regard 
 as abnormal being the elevation of the nervous layers here and there 
 into folds, the disposition of which is mainly meridional. In the other 
 examples (Nos. 3, 4, 5, 6 and 10) a greater or less degree of separation has 
 taken place between the nervous and pigmented layers of the retina. 
 This natural form of dissection is not without its advantages, since it 
 enables us to estimate more accurately the varying degrees of thickness 
 of the nervous layer in different situations. 
 
 All the specimens show that the pars optica retinae is thickest at its 
 junction with the optic nerve, where on an average it measures 0-56 mm. 
 in thickness. As it spreads out over the posterior surface of the cavity 
 of the eyeball it gradually thins, till at the equator it measures no more 
 than 0-18 mm. in thickness; in front of this its gradual attenuation con- 
 tinues until it ends abruptly in the region of the ora serrata, where it 
 is about o-i mm. thick. At the point where the retina becomes con- 
 fluent with the optic nerve, there is in correspondence with the centre 
 of the optic nerve a little pit or depression, the physiological excavation 
 or cup, surrounded by a slightly everted circular lip, formed by the con- 
 verging nerve fibres as they pass over the edges of the tunics of the 
 eye surrounding the inner circumference of the foramen opticum sclerae. 
 
 It is this arrangement which gives rise to the slight circular eleva- 
 tion (about 1-5 mm. in diameter) of this part above the level of the 
 surrounding retina, and hence justifies the name of optic papilla 
 frequently applied to it, though it is only fair to say that the existence 
 of this projection is denied by many, and is accounted for as being an 
 optical illusion. An inspection of the various photographs in which 
 this region is displayed appears, however, to justify the conclusion that 
 the slight elevation referred to is determined by the structural arrange- 
 ments of the parts. (See further, p. 57.) 
 
 About 3 mm., or a little over, to the lateral or temporal side of the 
 optic nerve in the horizontal plane lies the macula lutea, within which 
 is a depression, called thefovca centralis, formed by the thinning of the 
 
22 ANTERO-POSTERIOR SECTIONS OF THE EYE 
 
 layers of the retina, so as to leave here only the cones and their 
 associated cells. The appearance and position of these parts will be 
 better understood when the fundus of the globe is examined (see p. 59), 
 but in meridional sections their position may also be made out. 
 Unfortunately, after death the retina in this region undergoes usually 
 a tumefaction of its layers, so that the position of the macula is 
 generally recognized by the presence of a pronounced fold extending 
 outwards from the papilla optica for the space of 5 mm. or so, having 
 at a point about 3 mm., or a little over, from the centre of the optic disk 
 or papilla a distinct dimple or depression. The latter indicates very 
 precisely the position of the fovea centralis. To this fold the name 
 plica centralis was applied, and it was formerly described as a normal 
 condition of the retina ; now, however, it is recognized as a post- 
 mortem change, induced no doubt by the more ready absorption of 
 fluids by this part of the retina. The two conditions are very clearly 
 shown in the photographs, Nos. 58 and 59 ; in the first of which the 
 fundus was photographed in the fresh condition, twenty minutes after 
 removal during life, whilst in No. 59 the same specimen was photo- 
 graphed after subjection to the influence of a 4 % hardening solu- 
 tion of formalin. Though the fold is not here present in its most 
 typical form, the reader will have no difficulty in recognizing the 
 altered appearance due to the swollen and oedematous condition of 
 the parts. 
 
 In the meridional sections the disposition of the fold will vary 
 according to the plane in which the section is made. Thus, if the 
 section be a horizontal one (see No. i), the fold will stretch from the 
 outer side of the optic nerve towards the posterior pole, coincident with 
 which, or nearly so, the fovea centralis is placed ; whilst, if the section 
 be vertical, the fold will be seen to pass at right angles to the plane of 
 the section towards the temporal or outer side of the fundus, as is 
 shown in Nos. 3, 4, and 6 an arrangement which enables us to dis- 
 tinguish the lateral or temporal from the mesial or nasal half of any 
 eye examined, though unfortunately we are not able, without further 
 data, to say definitely whether the eye belongs to the right or left side. 
 
 From the optic entrance to the ora serrata and in front as far as the 
 ciliary processes, the retina is spread out and forced against the middle 
 coat by the pressure exercised by the vitreous humour, the external 
 investing membrane of which the hyaloid membrane is everywhere 
 in contact with the inner surface of the retinal layers. It is not easy 
 in all the sections to make out the existence of this hyaloid membrane 
 as an independent layer, but in No. 10 quite a good view of it is 
 obtained, where to the right side of the entrance of the optic nerve it 
 has in part become separated from the inner surface of the underlying 
 retina. 
 
ANTERO-POSTERIOR SECTIONS OF THE EYE 23 
 
 The ora serrata, as has been stated, marks very definitely the 
 anterior limit of the visual retina the pars optica retinae. In front of 
 this border the retina, no longer composed of nervous elements, is con- 
 tinued forwards as the thin cellular layer, the pars ciliaris retinae, which 
 in conjunction with the pigment layer overlies the inner surface of the 
 ciliary body. 
 
 As a rule, the ora serrata is situated 6 mm. behind the external sclero- 
 corneal junction. It displays a variety of form, as may be seen in the 
 different photographs, Nos. i to 10, but in all there is evidence that this 
 edge of the nervous retina is here more firmly connected with the sub- 
 jacent layers, for, as may be seen by an inspection of the specimens, 
 although the pars optica retinae tends to separate readily from the 
 underlying pigment layer behind this margin, this separation never 
 takes place in front of it. This condition is further emphasized by the 
 fact that just at this edge the pars optica retinae, owing, it may be, 
 to the action of post-mortem changes or the influence of the hardening 
 reagent, tends to form a swollen fold along this margin, as may be 
 well seen in Nos. 2, 10 and 14. In other examples, however (Nos. 7, 
 8 and 9), though similarly treated, this appearance is not displayed. 
 Careful measurement reveals the fact that the ora serrata reaches 
 further forwards on the nasal than on the temporal side of the globe. 
 Thus the average distance of the ora serrata from the corona ciliaris on 
 the medial side of the eye is 3-3 mm., whilst on the lateral aspect of the 
 globe the mean distance between these two structures is 4-2 mm. 
 
 In some of the specimens the ora serrata displays a scalloped edge 
 (Nos. 5, 7 and 14). Here the margin is interrupted by a series of pointed 
 processes separated by backwardly directed concave notches. From 
 the pointed processes there occasionally extend forwards on to the 
 orbiculus ciliaris for a variable length thin white lines; these lines, 
 when present, are usually directed towards the valleys or intervals 
 between the ciliary processes, or it may be to smaller ciliary folds 
 which lie between the larger ones. Oftentimes a more deeply pig- 
 mented strand replaces the white thread-like bundle, passing forwards 
 from the points of the serrated edge of the ora. If in an orbiculus 
 which has been dissected off from the scleral coat these be viewed by 
 strong transmitted light, the darker radial strands will be seen to corre- 
 spond to leashes of fine vessels, often with a larger one in their centre, 
 passing back from the ciliary processes or the intervals between them. 
 
 It is also noteworthy that the spiny appearance imparted to the edge 
 of the ora serrata by the presence of these pointed processes is always 
 better seen on the nasal side, where the orbiculus is narrower, than on 
 the temporal side, where the ora serrata usually displays a more even 
 appearance. Indeed, it is not at all uncommon to find evidence of the 
 pointed processes only along the nasal side of the edge of the ora. 
 
24 ANTEROPOSTERIOR SECTIONS OF THE EYE 
 
 More commonly, too, they are best seen in young adults, and seem to 
 tend to disappear in the eyes of older subjects, the ora serrata then pre- 
 senting a more even appearance such as is displayed in Nos. 2, 8 and 9. 
 The photograph, No. 9, is that of a pathological specimen, introduced 
 into the series for another purpose, but it exhibits a remarkably even 
 ora serrata and is here noticed on that account. 
 
 The number of these pointed processes is extremely variable ; in 
 some they are large and well-pronounced, as in Nos. 7 and 14 ; in others 
 they are smaller and more numerous, as in No. 10. As many as 34 
 have been counted; in other cases only 17 or 18 have been noticed, 
 whilst in some instances it has been impossible to recognize their 
 presence at all. 
 
 What strikes one first on examining the pars optica retinae in the foetal 
 eye (Nos. 15, 16, 17 and 18) is the apparent redundancy of this layer. 
 Whether this condition is more apparent than real it is difficult to say, 
 as possibly the relatively thicker and softer character of the tissue may 
 render it more susceptible to post-mortem changes ; but in most of the 
 specimens examined the appearance suggests that the retinal layers are 
 not yet adequately stretched over the inner surface of the vascular 
 and protective coats of the eye, which would seem to indicate that the 
 expansion of the retina over the inner surface of the globe was not 
 completely effected by its own intrinsic growth, but rather by 
 a stretching and spreading out of its layers on the inner surface of the 
 growing and expanding chorioid and sclera. Support is given to this 
 view by the ophthalmoscopic examination of the eyes of young children, 
 in whom the ' watered silk ' appearance displayed by the retina is 
 accounted for on the supposition that that membrane is not yet evenly 
 stretched over the fundus, but is thrown into folds. 
 
 As has been said, in briefly describing the development of the retina 
 (p. 19), at the level of the ora serrata the inner lamella of the optic cup 
 undergoes a rapid transition in structure. The nervous elements dis- 
 appear, and all that remains to represent this wall is a thin lamina com- 
 posed of a single layer of columnar cells which now becomes intimately 
 connected with the externally placed pigment layer, from which it can, 
 only with difficulty, be separated. We are not here concerned with 
 a consideration of the question what element in the retina is represented 
 by this layer of cells which constitutes the pars ciliaris retinae. It is 
 sufficient for our purpose to note that as we trace this layer forwards it 
 undergoes a gradual thinning, involving a reduction in the length of the 
 columnar cells, so that, whereas in the immediate vicinity of the ora 
 serrata these cells are of considerable height (the figures given are from 
 0-040 to 0-050 mm.), we find on examining them as they overlie the ciliary 
 processes that they only measure 0-015 mm - T ne mner surface of this 
 layer has been described as forming a glassy membrane, the membrana 
 
ANTERO-POSTERIOR SECTIONS OF THE EYE 25 
 
 limitans ciliaris. The exact nature of this layer is not well under- 
 stood, but its interest from the present standpoint is based upon the fact 
 that it affords a means of attachment to the fibres and lamellae which 
 stretch from the ciliary body towards the lens, forming the zonule of 
 Zinn. 
 
 T\\Q pars iridica retinae is merely the forward extension of the pars 
 ciliaris retinae lining the inner surface of the pigment layer which 
 clothes the posterior surface of the iris ; at the pupillary edge of the iris 
 these two layers become structurally continuous with each other by a 
 folded edge, which, in the adult, represents the rim of the secondary 
 optic vesicle or cup. The cells of the layer forming the pars iridica 
 retinae have, however, lost the columnar arrangement characteristic of 
 the pars ciliaris retinae, and now exhibit a more cubical form. As they 
 pass on to the posterior surface of the iris they become loaded with 
 pigment, so that it is impossible to distinguish them from the pigment 
 layer proper of the retina upon which they rest. 
 
 The pigment layer of the retina. Sufficient reasons have been 
 already advanced for regarding this layer as morphologically a part of 
 the retina, since, as has been shown, it is developed from the outer wall 
 of the ectodermic optic cup. Nor need much space be devoted to 
 its description, for in describing both the nervous retina and the 
 chorioid it has been repeatedly referred to as occupying a position 
 intermediate between these two structures. 
 
 Its tendency to adhere to the chorioid has also been alluded to, 
 a tendency which involves its separation from the layer to which it more 
 properly belongs, viz. the pars optica retina. The probability of the 
 existence of a lymph space between these two lamella has also been 
 referred to, and it has been pointed out that in the fully developed eye 
 this cleft represents the cavity of the primary optic vesicle. 
 
 The pigmented layer of the retina lines the whole of the interior of 
 the uveal tract from the entrance of the optic nerve to the pupillary 
 margin of the iris ; internally it is overlain by the pars optica retinae as 
 far forwards as the ora serrata, in front of which, in the hardened and 
 fixed eye, its colour is revealed through the thin pars ciliaris retinae, 
 whilst where it passes over the back of the iris its intensity of colour 
 is reinforced by the pigment within the cells of the pars iridica retinae, 
 which is in contact with it. As has been said, although the connexion 
 between this pigmented layer of the retina and the pars optica is feeble 
 and easily ruptured, its union with the pars ciliaris and iridica is much 
 more complete and difficult to separate. For further details concerning 
 the retina see pp. 44, 56. 
 
 The lens. In meridional sections of the eyeball the lens appears 
 suspended within the cavity of the globe in such a position as to seem 
 to plug posteriorly the pupillary aperture; it is thus brought into 
 
26 ANTERO-POSTERIOR SECTIONS OF THE EYE 
 
 relation with the iris, which touches it tangentially in front ; its circum- 
 ference is directed towards the blunt projecting ends of the ciliary 
 processes, from which, however, it is separated by the circumlental 
 space, the width of which as a rule averages about i mm. 
 
 It is here that by careful inspection and the use of suitable light one 
 may observe the arrangement by which the lens is suspended and 
 held in position. A good view of this, which constitutes the suspensory 
 ligament oi the lens or zonule of Zinn, is seen in No. 8 and also in No. 9. 
 The latter, which is from a pathological preparation in which the entire 
 iris is adherent to the posterior surface of the cornea, is included, since 
 the iris being pulled forward permits the better illumination of the 
 ligament, which in this case is not lying in shadow behind the iris. 
 The same appearances are faintly seen in Nos. 2 and 4. Behind, the 
 lens rests on the anterior surface of the vitreous humour, in a shallow 
 depression called the fossa patellaris or hyaloid fossa. Opinions differ 
 as to whether or no this fossa is lined by an extension of the hyaloid 
 membrane. My own observations confirm the views of Stuart that the 
 membrane is continuous over the surface of the fossa. The prepara- 
 tions on which this conclusion is based are not here represented, but 
 in No. 8 there is evidence to show that the hyaloid membrane on the 
 left side of the section is separate from the suspensory ligament, whilst 
 in No. 10 the same arrangement would seem to be suggested. But 
 perhaps the best demonstration of the independence of this layer from 
 the suspensory ligament is given in No. 9, where it may be seen 
 distinctly passing behind the lens. Unfortunately, the preparation is 
 taken from a pathological eye, but in this instance that does not invali- 
 date the proof which it exhibits. 
 
 It is in the centre of the bottom of this saucer-shaped depression 
 that the anterior extremity of the hyaloid canal opens : here it is some- 
 what enlarged, forming what is known as the post-lental space. A 
 suggestion of this may possibly be seen in No. 15, the eye of a full- 
 term foetus. 
 
 What most attracts attention concerning the lens, in the series of 
 meridional sections of the eye, is the fact that its form varies very 
 much. As we pass from the foetal form (Nos. 15, 16 and 17) to that 
 displayed in advanced life (Nos. i and 2), it is evident that the degree 
 of convexity of the anterior surface of the lens displays a marked reduc- 
 tion. During foetal life the lens approaches more nearly the spherical 
 form ; in the aged it becomes thinner and of more compressed shape. 
 This appears to be effected at the expense more particularly of its 
 anterior surface, which becomes flattened, an appearance which is 
 particularly well seen in Nos. i and 2, where the anterior aspect of the 
 lens has practically become a plane surface. Intermediate forms are 
 displayed in Nos. 3, 4, 5, 8, 10 and n. What appears noteworthy is 
 
ANTERO-POSTERIOR SECTIONS OF THE EYE 27 
 
 that this reduction in the anterior curvature takes place evenly and 
 uniformly throughout, and not, as will be presently referred to, un- 
 equally, as appears to happen in the case of the posterior surface. 
 
 If the posterior aspect of the lens be examined in all the photo- 
 graphs reproduced, with the exception of those of the foetal eyes, the 
 curvature of this surface is always more pronounced in the centre than 
 towards the circumference. Whether this is a natural appearance or due 
 to the influence of the hardening reagent it is difficult to say. The fact 
 that the more pronounced central convexity corresponds to the denser 
 nuclear part of the lens, whilst the flatter circumferential part coincides 
 with what is termed the substantia corticalis, the softer and more com- 
 pressible part, would seem to suggest that the forms represented in the 
 photographs are unnatural, and the results of the irregularities pro- 
 duced by the hardening reagents. If this be so it is a proof that, taken 
 as a whole, the lens is more plastic around its circumference just where 
 it is most subject to the influence of the suspensory ligament. Another 
 feature which seems important is that this circumferential flattening of 
 the posterior surface of the lens only affects that part of it which lies 
 wide of the area of its normal optical efficiency. As a consequence of 
 the forms here described it follows that the equator of the lens does 
 not, as one is led to believe, correspond to a linear strip coinciding 
 with the summit of its greatest width, but harmonizes with a somewhat 
 broad and flattened zone, which intervenes between the attachments of 
 the anterior and posterior lamellae of the suspensory ligament. It is 
 this zone which forms the inner wall or base of the triangular space 
 which forms the so-called canal of Petit. The equatorial region of the 
 lens may therefore be described as that circumferential area which lies 
 between the attachment of the anterior and posterior layers of the 
 zonule of Zinn, the implantation of which on the capsule of the lens 
 is marked by two well-marked edges between which, as shown in 
 meridional section, the lens exhibits different degrees of flattening. 
 This is displayed in various forms in Nos. i, 2, 3, 4, 8, 9, 10 and n. 
 In No. 9 the flattening of the equatorial region is most marked, but this, 
 as has been already stated, is a pathological specimen, the result of 
 a wound of the cornea. It would appear from a consideration of these 
 observations that the influence exercised by the fibres of the suspen- 
 sory ligament are rather of the nature of a traction than a pressure 
 effect, since the former would tend to emphasize the presence of the 
 ridges which limit it in front and behind the equatorial zone, whilst 
 a pressure effect, squeezing upon the intervening tissue, would cause it 
 to bulge up into the floor of Petit's canal. 
 
 The lens, as measured in the specimens at my disposal, gives results 
 as follows : 
 
 The equatorial width varies from 8-0 mm. to 9-9 mm., yielding an 
 
28 ANTERO-POSTERIOR SECTIONS OF THE EYE 
 
 average of 8-6 mm. for the series, numbering fourteen in all. The antero- 
 posterior thickness varies both with age and the condition of accom- 
 modation, consequently we expect to find greater differences in this 
 measure. The figures deduced from the series range from 2 mm. 
 to 4 mm., with a mean for ten specimens of 3-02 mm. 
 
 The relations of the lens are well displayed in the photographs of 
 the meridional sections reproduced. Anteriorly the central part of the 
 lens forms the posterior wall of the anterior compartment of the aqueous 
 chamber; the extent of this surface depends on the size of the area 
 uncovered by the pupil. External to the pupillary margin, which rests 
 in contact with the anterior surface of the lens, the front of the lens as 
 far as the attachment of the anterior fibres of the zonule enters into the 
 formation of the posterior wall of the posterior camera of the aqueous 
 chamber. The extent of the surfaces of the iris and lens in contact 
 with each other is seen to vary in the photographs. It seems to depend 
 on the degree of tension of the iris and the extent of the curvature of 
 the lens. In some, as in No. 10, the area of contact corresponds to a 
 point, the edge of the pupillary margin, from which the iris extends tan- 
 gentially outwards ; in others, as in Nos. 3, 4 and 8, the two surfaces have 
 a wider area of contact ; whilst in Nos. i and 2 the two structures, owing 
 to the flatness of the front of the lens, lie parallel to each other in close 
 relation. In the preparations in my possession, the depth of the 
 anterior chamber, as taken from the central point of the inner 
 surface of the cornea to the front of the middle of the lens, measures 
 from 2 mm. to 3 mm., giving on an average a depth of 2-2 mm. 
 Equatorially the lens is related to the projecting rounded ends of the 
 ciliary processes, from which it is separated by the circumlental 
 space, the width of which I find to range from i mm. to i-i mm., 
 with an average of i-oi mm. This space, be it noted, is bridged across 
 by the fibres of the zonule of Zinn } which, as shown in Nos. 8 and 9, are 
 subdivided into two more or less well-defined laminae, between which 
 lies the interval known as the canal of Petit. This so-called canal is 
 triangular in meridional section ; the inner side or base, measuring on an 
 average about i mm., is formed, as has been stated, by the equatorial zone 
 around the circumference of the lens. Posteriorly the lens rests in the 
 fossa patellaris of the vitreous humour, and is thus brought into relation 
 centrally to the anterior extremity of the hyaloid canal. The equatorial 
 axis of the lens lies 2-4 mm. behind the limbus conjunctivae, or the 
 external sclero-corneal junction. 
 
 The most noticeable features in connexion with the foetal eye are 
 the large proportionate mass of the lens and its more spherical form. 
 In consequence, the anterior chamber is shallower, whilst the fossa 
 patellaris is deeper. The region of the equator corresponds to the 
 summit of the curve formed by the coalescence of the anterior and 
 
ANTERO-POSTERIOR SECTIONS OF THE EYE 29 
 
 posterior surfaces, and does not display any indication of those borders 
 to which the fibres of the zonule of Zinn are attached as in the adult. 
 The circumlental space is narrower, and in the earlier specimen 
 what corresponds to the ciliary processes appears to abut against 
 the circumference of the lens. 
 
 These details may be seen in No. 15, which is the eye of a full-time 
 foetus, and in Nos. 16 and 17, which are photographs of the eye of 
 a 6-|-months' foetus. 
 
 For further details concerning the lens see pp. 38, 45 and 50. 
 
 The zonule of Zinn. As has been stated in the foregoing descrip- 
 tion of the lens in these meridional sections, the suspensory ligament 
 of the lens, or the zonule of Zinn, is faintly seen in Nos. 2 and 4. The 
 difficulty in viewing it depends on the fact that it is far from easy 
 to get it suitably illuminated, since owing to the fact that it lies behind 
 the iris, it is apt to be thrown into shadow by that structure. In No. 8 
 these difficulties have been happily overcome, and on the left-hand 
 side of the specimen the arrangement of its fibres is well displayed. 
 Whilst not denying the existence of fibres which occupy an inter- 
 mediate position, or which cross each other, the preparation clearly 
 shows that the majority of the fibres of the zonule are arranged in two 
 lamellae. The anterior layer passes to be united to the capsule of the 
 lens in front of the true equator, where its attachment corresponds 
 to a fairly abrupt margin ; whilst, in similar fashion, the posterior sheet 
 of fibres passes to the back of the capsule, to which they are similarly 
 attached, along a more or less pronounced border just behind the 
 equator. The interval between the laminae, formed by the circumference 
 of the lens, has been described as the equatorial zone, and in the 
 different sections shown exhibits varying degrees of convexity, though 
 in the main a tendency to display a flattened form. As the fibres con- 
 stituting these layers arise from the ciliary processes, they appear to 
 spring in greater number from the valleys between the processes, and 
 here, being closer together, the two sheets separate as they cross 
 the circumlental space to reach the lens ; the anterior layer passing 
 inwards and slightly forwards, its lenticular attachment lying in the 
 same plane as the anterior curved edge of the bulging ciliary processes, 
 whilst the hinder lamina is recurved inwards and backwards, so as to lie, 
 where it is connected with the lens capsule, on a level with the spring 
 of the posterior border of the ciliary processes. In consequence of this 
 arrangement the interspace between the two layers displays a triangular 
 form, the base corresponding to the equatorial zone of the lens, whilst 
 the sides, both back and front, are formed by the diverging sheets 
 of fibres ; the summit of the triangle is obscured by the inward bulge of 
 the ciliary processes and, thus interrupted, will form a series of pointed 
 processes extending outwards in the valleys between the processes. 
 
30 ANTERO-POSTERIOR SECTIONS OF THE EYE 
 
 To this interspace has been given the name of the canal of Petit, 
 the nature of which will be more fully discussed when some of the 
 other photographs have been considered (see pp. 48 and 51). 
 
 In No. 8 it is worth noting that the posterior sheet of the fibres of the 
 zonule of Zinn is independent of the thin hyaloid membrane encasing 
 the vitreous, as may be faintly seen on the left side of No. 8, and also 
 on both sides in No. 9. This latter print, although from an injured eye, 
 has been introduced because it gives so excellent a view of the zonule, 
 owing to the fact that the iris, having become adherent to the cornea, 
 has been pulled forward, carrying with it the ciliary processes. In this 
 way a natural dissection of the parts has been the result, and the iris 
 being drawn out of the way the suspensory ligament of the lens is 
 more clearly exposed. 
 
 Stretching across the circumlental space the layers of the suspen- 
 sory ligament are seen to intervene between the aqueous chamber in 
 front and the vitreous behind. The anterior layer of the zonule forms 
 in part the hinder wall of the posterior camera of the aqueous chamber, 
 being separated from the posterior surface of the iris by an interval 
 averaging 0-93 mm. from before backwards, a measure which indicates 
 the depth of the posterior chamber at this particular part. The dis- 
 tance from the back of the iris to the front of the posterior layer of the 
 zonule measures on an average 1-9 mm. This includes not only the 
 posterior chamber, but also the so-called canal of Petit. 
 
 For further details concerning the suspensory ligament see 
 PP- 37, 47 and 50. 
 
 The vitreous. Owing to the apparently structureless nature of this 
 constituent of the eyeball, but little evidence of its presence can be seen 
 in the photographs. Its existence is demonstrated in most of the prints 
 by the presence of particles of dust which have become embedded in it, 
 or by the air bubbles within its substance which tend to make their 
 appearance in the preparations when they are being thawed after having 
 been cut in the frozen condition. 
 
 The vitreous is enclosed in the hyaloid membrane, the outer surface 
 of which is closely applied to the inner surface of the retina. Under 
 ordinary circumstances in these meridional sections there is no evidence 
 to prove the existence of this layer, but exceptionally, as in No. 10, the 
 hyaloid membrane has become separated from the retina, and appears 
 as a delicate filmy structure lying in front of the retina to the right of 
 the entrance of the optic nerve ; the delicate strands of tissue which 
 connect the two are distinctly noticeable. In the same preparation the 
 hyaloid membrane is seen separated from the surface of the ciliary pro- 
 cesses on the left side of the section. 
 
 Attention has been already directed to the fact that in Nos. 8 and 9 
 the hyaloid membrane has also been shown as distinct from the posterior 
 
ANTERO-POSTERIOR SECTIONS OF THE EYE 31 
 
 lamina of the fibres of the suspensory ligament, from which it stands as 
 a layer apart. 
 
 In the foetal eyes, the vitreous displays more evidence of structure, 
 particularly in the earlier stages. In the full-time foetus, No. 15, the 
 vitreous has shrunk away from the retina posteriorly. A suggestion of 
 a post-lental space in the centre and at the bottom of the patellqr fossa 
 also appears visible. 
 
 In the foetal eyes of 6| months the vitreous is traversed by layers 
 of filmy-looking tissue, and does not appear to fill up the entire space 
 within the retina. This is probably due to irregularity in the shrinkage. 
 In No. 17 the hyaloid artery can be very clearly seen passing through 
 the substance of the vitreous from the optic papilla posteriorly to the 
 back of the lens in front. 
 
 For further details concerning the vitreous see pp. 48 and 61. 
 
CHAPTER II 
 
 DISSECTIONS OF THE EYE FROM THE FRONT 
 
 THIS includes the series of photographs from Nos. 19 to 32 inclusive. 
 These comprise an illustrative series of dissections designed to expose 
 the different structures in relation to the aqueous chamber. 
 
 In No. 19 the anterior surface of the globe of the eye is exposed. 
 The cornea has been removed by cutting it through along the line 
 of the sclero-corneal junction. Wide of this the scleral conjunctiva is seen 
 in situ, displaying a cut edge externally where it has been snipped 
 through ; beyond this, the external surface of the sclerotic, cleared of 
 its muscular attachments, is shown. 
 
 By the removal of the cornea the anterior camera of the aqueous 
 chamber has been laid open, and the structures which form its posterior 
 boundary are thus exposed. These are, within the area of the pupil, 
 the anterior surface of the lens, and, external to the pupillary margin, 
 the anterior surface of the iris, which is here displayed. 
 
 In another preparation, No. 20, the dissection has been carried a stage 
 further, so as more fully to expose the iris and its attachments. Here 
 the sclera has been stripped off from the front of the eye, exposing the 
 outer surface of the ciliary body and chorioid] but be it noted that in 
 tearing away the sclerotic a narrow ring of condensed tissue, the so- 
 called annular ligament, has been left : this is seen just where the iris 
 and the ciliary body become confluent, and is well displayed in the 
 upper half of the left side of No. 20. where the arrangement of the 
 light throws it into relief. This is the structure to which the meridional 
 fibres of the ciliary muscle are attached, and it is from the front of this 
 ridge that the fibres of the pectinate ligament have been torn away in 
 removing the sclerotic and cornea. The reader should remember that 
 it is this ring of tissue which in microscopic meridional sections of this 
 region forms the projecting process called the scleral process or spur, 
 and that the canal of Schlemm lies immediately to the outer side of this 
 ring of condensed tissue, and has necessarily been laid open by the 
 removal of the sclera, since, as has been stated (p. 17), the outer wall of 
 Schlemm's canal is formed by the dense scleral tissue, whilst its inner 
 wall is constituted by the loose trabecular substance of the pectinate 
 ligament. 
 
 The anterior surface of the iris is well displayed in both Nos. 19 and 
 20. In the hardened condition, in both these preparations, the iris appears 
 thicker around the pupil, where it forms a smooth elevated ring crossed 
 
DISSECTIONS OF THE EYE FROM THE FRONT 33 
 
 transversely by a number of radial folds. This appearance of thickness 
 is due to an actual increase in the thickness of the tissue of the iris 
 in this region, as may be seen in the meridional section, No. 4 ; but may 
 possibly be exaggerated by the bending between that part which is in 
 contact with the lens and the portion which lies circumferentially, as 
 shown in No. 3. This appearance is further enhanced by the inward 
 slope of the iris towards the pupillary margin, which has a thin chisel- 
 like edge, the margin of which is finely notched, and exhibits a narrow 
 black border. In No. 20, close to the pupillary edge, the constituent 
 fibres of the iris are seen arranged in a festooned or arcaded fashion, 
 within which, here and there, are seen small depressions leading into 
 the stroma of the iris. These are regarded by Fuchs as the stomata of 
 lymph canals. 
 
 Sometimes, as shown in Nos. 21 and 22, about 0-5 mm. from the pupil- 
 lary margin, the iris exhibits at different points what appears like a 
 free edge of tissue. The same may be seen in meridional section in 
 Nos. 7 and 10, where it presents the appearance as if the iris were 
 composed of two strata, one terminating in the pupillary margin, 
 the more superficial layer ending, as has been described, in a free edge 
 a little without and in front of the pupil. The interest attaching to 
 this particular arrangement is that the position of this irregular edge 
 marks the line of attachment to the iris of the pupillary membrane 
 which existed at an earlier period of development, as may be seen in 
 meridional section in No. 16. The pupillary stomata aforementioned 
 lie to the inner side of this attachment, and thus provision is made 
 whereby filtration of the contents of the posterior camera of the 
 aqueous chamber may take place prior to the opening up of the 
 communication through the pupil with the anterior chamber. 
 
 The radial folds which traverse the iris are determined by the 
 vessels and nerves of the iris which form the elevations between them, 
 as is demonstrated in No. 26, where the arrangement of these structures 
 is well displayed, but no doubt towards the pupillary margin contraction 
 folds are also present. 
 
 Wide of the smooth elevated zone already referred to, the iris 
 exhibits a number of concentric folds, intensified during dilation of the 
 pupil, and obviously produced by the contraction and wrinkling of the 
 tissues. At its periphery the iris undergoes a change in its appearance 
 and structure ; its surface becomes irregular, pitted, and depressed. In 
 the accompanying photographs, Nos. 19, 20 and 26, in which the cornea 
 and sclera have been removed, it will be recognized that the ciliary 
 attachment of the iris corresponds to the bottom of the iridial or 
 filtration angle. As will be seen, its connexion with the ciliary body 
 lies immediately to the inner side of the annular ligament, the ring 
 of condensed tissue which on meridional section forms the scleral spur. 
 
34 DISSECTIONS OF THE EYE FROM THE FRONT 
 
 Bearing in mind the connexions of the pectinate ligament, as have been 
 described (see p. 17), it will be obvious that the internal fibres of that 
 structure, as they pass on to the circumference of the iris, will have 
 been torn in the removal of the cornea, and one would expect 
 evidence of this, as may be seen in No. 20, where some of the torn 
 ends of these ruptured fibres are distinctly visible. Just within the 
 annular ligament are a number of crypts, the orifices of which are inter- 
 sected by a number of delicate fibres. The depressions into which these 
 crypts open correspond, as may be observed in No. 26, to the intervals 
 between the elevations caused by the bundles of vessels. It is through 
 these crypts, sometimes called the ciliary stomata of the iris in contra- 
 diction to the pupillary openings already referred to, that the anterior 
 chamber communicates with the spaces of Fontana which are disposed 
 around the bottom and outer wall of the filtration angle. 
 
 An examination of the anterior aspect of the iris, as displayed in 
 photographs, Nos. 19, 20, 21 and 26, proves that this surface of the iris 
 exhibits considerable differences in different individuals. Apart from the 
 question of pigment, it will be seen that in No. 21 the anterior surface 
 appears much more rugged than any of the others, there being several 
 large depressions on it, the edges of which are sharp and well defined ; 
 here, too, near the pupillary margin there is an irregular border, the 
 margin of which appears free and outstanding. This arrangement has 
 been alluded to already. In No. 26 the front of the iris is shown as 
 much more regular. Owing to the absence of pigment, the radial 
 arrangement of the vessels and nerves is well seen. The crypts at 
 its ciliary border are not so well defined, but here and there the torn 
 fibres of the pectinate ligament are indicated by the woolly appearance 
 imparted to this edge. 
 
 In No. 24 the dissection has been carried farther by the removal of 
 one half of the iris. In this way the posterior camera of the aqueous 
 chamber has been laid open by the removal of its anterior wall, thus 
 fully exposing the structures which form its posterior boundary. 
 Viewed in the stereoscope the right side of the photograph displays the 
 anterior surface of the lens now fully exposed. A small quantity of 
 pigment close to the pupillary edge of the divided iris shows where 
 that structure has rested in contact with the lens. The circitmlental 
 space is revealed as a dark ring round the lens. Crossing this, in 
 radial fashion, the delicate fibres of the zonule of Zinn are to be seen. 
 Where these are attached to the lens capsule they impart a crenated 
 appearance to the circumference of the lens. In front of these, which 
 form the anterior layer of the suspensory ligament of the lens, and about 
 0-5 mm. from the periphery of the lens, may be seen the rounded knob- 
 like extremities of the ciliary processes. Anterior to these are a number 
 of thin, projecting, light-coloured folds. These are even better dis- 
 
DISSECTIONS OF THE EYE FROM THE FRONT 35 
 
 played in No. 25, where the entire iris has been taken away. It is 
 evident that these folds have been divided when the iris has been 
 removed, and consequently one would expect to see evidence of their 
 continuity on the back of the iris, as may be seen, here and there, in 
 No. 23. It is difficult to say whether these folds correspond to the 
 ciliary processes, or whether they alternate with them. The appear- 
 ance displayed would seem to indicate that they were a forward 
 extension of these processes. Their number is approximately sixty- 
 eight to seventy, which would bring them into harmony with the 
 number of ciliary processes in the corresponding specimen. The 
 presence of these folds must cut up the posterior camera into a series 
 of compartments corresponding to the intervals between them, and 
 those who deny the existence of a posterior chamber will have to 
 account for the disappearance of these interspaces by the compression 
 of the folds against the anterior surface of the lens and the projecting 
 fore parts of the ciliary processes. 
 
 It may be well now to examine the posterior surface of the iris. This 
 is exposed in the separated iris shown in No. 23. Owing to the deeply 
 pigmented condition of this side of the iris, it is extremely difficult to get 
 a photograph of it which will show up the detail. In this preparation, 
 however, the fluted and folded arrangement of the back of the iris is 
 fairly well seen. The appearance, however, is better displayed in No. 46, 
 where the iris is represented in situ along with the corona ciliaris. Here, 
 owing to the bleaching action of peroxide of hydrogen, its structural 
 details are better displayed. Around the pupillary margin there is a 
 zone about i mm. in width, in which the posterior surface of the iris is 
 thrown into a series of very fine radial folds. These overlie the part of 
 the iris in which the sphincter muscle of the pupil is placed, and form 
 the contraction folds of the pupillary zone (Schwalbe). A careful exami- 
 nation of the pupillary edge, as displayed in No. 23, will prove that this 
 margin is not an evenly flowing line, but exhibits a crenated appear- 
 ance due to the projecting rounded ends of these fine folds. 
 
 Wide of the pupillary zone (No. 46), the structural folds of Schwalbe, 
 much more pronounced in form, are seen to radiate outwards towards the 
 ciliary attachment of the iris, where they both widen and deepen, giving 
 to this aspect of the iris a pleated appearance. It is these folds which 
 we have already noticed in a divided condition in the dissections where 
 the iris has been removed (Nos. 24 and 25). 
 
 The magnification in No. 46 is not sufficient to reveal the concentric 
 folds described by Fuchs, though some suggestion of them may be 
 recognized in the right-hand lower quadrant of the iris. 
 
 The iris measures on an average n mm. in diameter; the diameter 
 of the pupil ranges from 3 mm. to 5-9 mm. in my preparations. 
 
 For other details in connexion with the iris see pp. 13 and 43. 
 
 C 2 
 
3 6 DISSECTIONS OF THE EYE FROM THE FRONT 
 
 Returning to a further examination of the dissection displayed in 
 No. 20, it will be seen that, surrounding the annular ligament, there is 
 a light-coloured circular zone about 2 mm. in width, the convex surface 
 of which presents a fine fluffy appearance. This is the outer surface 
 of the ciliary body, and corresponds directly to the external portion of 
 the meridional fibres of the ciliary muscle. Externally, it has been 
 separated from the sclera, which has been removed. Passing to this 
 zone may be seen the filaments of the ciliary nerves, together with 
 branches from the anterior and long posterior ciliary arteries. 
 
 Wide of this ciliary zone the outer surface of the chorioid is exposed, 
 overlain by some of the ciliary nerves and exhibiting the whorl-like 
 arrangement of the radicles of the vorticose veins. In No. 25 a further 
 dissection of this region has been displayed in this preparation ; the 
 tissue comprising the ciliary muscle has been stripped off on the left- 
 hand side of the photograph. The cut edge of the muscle is seen 
 at the right and lower corner of the preparation. Here the tissue 
 removed includes both the meridional and circular fibres of the ciliary 
 muscle, but as the strip has been pulled away, an ever-increasing number 
 of the circular and finally some of the radial fibres have remained 
 in situ, so that the transition from complete absence to presence of the 
 entire muscle is a gradual process, as may be recognized by examining 
 the upper part of the preparation. A portion of the strip removed is 
 seen stretched out in No. 66. It gives an admirable view of the ciliary 
 plexus (plexus gangliosus ciliaris) formed by the splitting up of the 
 ciliary nerves. The same photograph displays a thin and delicate 
 membrane which, from the fact that it lies within the plane occupied 
 by the ciliary nerves and has been removed without carrying with it 
 any trace of the vascular chorioid, must be regarded as the lamina 
 suprachorioidea, a point of some interest, as this would appear to 
 suggest that such may be the main insertion of the meridional fibres of 
 the ciliary muscle. 
 
 Returning to a further consideration of the dissection displayed 
 in No. 25, it will be observed that the outer surface of the orbiculus 
 and corona ciliaris has been exposed by the removal of the ciliary 
 muscle. This, as has been explained, is most complete in the lower 
 part of the preparation. The most noticeable feature in connexion 
 with the surface thus exposed is the fact that the vessels of the 
 chorioid, as now exhibited, display an arrangement of parallel bundles 
 meridional in their disposition, thus contrasting with the appearance of 
 the vorticose veins which lie wide of the ciliary zone. These groups 
 of vessels appear to correspond with the position of the ciliary processes 
 which lie internal to them. 
 
 If the photograph (No. 25) be examined immediately to the left of 
 the cut edge of the ciliary muscle, the surface from which the muscle 
 
DISSECTIONS OF THE EYE FROM THE FRONT 37 
 
 has been removed appears as a well-marked groove. The deepest part 
 of the groove lies immediately outside the roots of the divided struc- 
 tural folds of the iris, and immediately in front of the free rounded ends 
 of the ciliary processes. It is here that the circular fibres of the ciliary 
 muscle lie, and it is against these structures that the compressing action 
 of the muscle must necessarily be exercised, thus leading fb consider- 
 able alterations in the posterior chamber, and so reducing its capacity, 
 at the same time forcing inwards the ciliary attachment of the iris, and 
 so stretching and opening up the filtration angle which lies in front of 
 this part of the iris. 
 
 The account of the ciliary muscle as seen in meridional section will 
 be found on p. 18. 
 
 Nos. 27 to 32 inclusive are designed to show the zonule of Zinn 
 under different conditions of light. In all, the cornea, iris, and part 
 of the sclerotic have been removed, so as to expose fully the lens, 
 the circumlental space, and the ciliary processes. In each case the 
 globe of the eye had been divided equatorially, so that it was possible 
 to view the structures as seen from the front either by reflected or 
 transmitted light, or by a combination of both. What is character- 
 istic of them all, with the exception of the preparation taken from the 
 eye of an eighth-month foetus (No. 32), is that the circumference of 
 the lens is not an evenly flowing outline, but is toothed and irregular 
 where some of the zonular fibres are attached to its capsule. The 
 appearance displayed is indicative of the strain exercised by these 
 fibres. In every case the fibres of the zonule as they stretch across 
 the circumlental space are represented in a state of tension ; in no 
 instance is there any indication that the fibres are relaxed. Nor, 
 though the fibres appear to be grouped in bundles, is it possible to say 
 from these photographs whether they arise from the valleys between 
 the ciliary processes or no ; all that can be asserted is that they are 
 placed at some little distance behind the rounded extremities of the 
 ciliary processes. No. 27 has been photographed under a combination 
 of reflected and transmitted light ; in it the fibres of the zonule stand 
 out as dark strands ; above and to the right there appears within the 
 zonule a darker zone, the significance of which is undetermined ; below 
 and to the left there is a certain amount of delicate fluffy tissue, as if 
 entangled amongst the fibres of the zonule. It will be quite evident 
 when viewed stereoscopically that the fibres of the suspensory liga- 
 ment do not lie on the same plane. No. 28 is a photograph of another 
 preparation taken by reflected light alone. In this the zonular fibres 
 appear as faint pale striae, some of which may be traced for a short 
 distance on to the front of the lens ; a point of interest is, that on the 
 left side in this preparation the lens casts a shadow on to the surface 
 of the vitreous, thereby indicating the presence of a membrane, and 
 
3 8 DISSECTIONS OF THE EYE FROM THE FRONT 
 
 proving the existence of a space between the structure which throws 
 the shadow and that on which it falls ; some of the fibres of the zonule 
 lie clearly in front of the shadow. 
 
 In No. 29, the same preparation as No. 28, viewed by a combination 
 of transmitted and reflected light, the striae of the zonule are but faintly 
 represented; the same observation holds good of No. 30, which is 
 a photograph of the same preparation viewed by transmitted light only. 
 
 In No. 31 an enlarged view of the same structures is shown ; the 
 only detail which need be referred to is, that the ciliary processes at the 
 lower part of the preparation cast a shadow on the front of the zonule 
 in such a way as to suggest that it forms a continuous membrane. 
 
 No. 32, from the eye of an eighth-month foetus, has been taken with 
 a combination of reflected and transmitted light. The fibres of the zonule 
 show up well, but their connexion with the lens is devoid of the spine- 
 like processes so common in the adult specimens. This would seem to 
 point to the fact that the occurrence of these irregularities in the 
 circumference of the lens in the adult is associated with the traction 
 effects exercised by the fibres of the zonule during the practice of 
 accommodation. Note the greater anterior convexity of the lens as 
 contrasted with the other preparations. 
 
 For further references to the suspensory ligament see pp. 13, 29, 
 47 and 50. 
 
 The Lens. In the various preparations which have been studied 
 the anterior surface of the lens is, in part or in whole, exposed exhibit- 
 ing in divers forms the appearance of the lens stars under different 
 conditions of light. In No. 20, as seen through the pupil, the anterior 
 surface of the lens exhibits a star form, of rosette appearance, with five 
 petals ; in No. 19 an indication of wedge-shaped masses meeting at 
 the centre is suggested ; whilst in No. 26 the division of the lens by 
 a tri-radiate series of dark lines is clearly seen. In the preparations 
 where the anterior surface of the lens is entirely exposed, dark, narrow, 
 wedge-shaped masses are displayed : these vary in number from ten 
 to thirteen. The bases of the wedges, which are of rounded form, 
 approach the circumference, whilst their apices are directed to the 
 centre of the lens (see Nos. 25, 27, 28, 29 and 31). In No. 32, from 
 the eye of an eighth-month foetus, these wedges are not revealed by 
 differences in tone ; here the front of the lens is traversed by four dark 
 lines, which meet in H-shaped fashion in the centre of the lens, and 
 divide it up into four unequal parts. 
 
 In most of the preparations the front of the lens retains some of the 
 iridial pigment on it, marking precisely the line of contact of the pupil- 
 lary margin at the time of death. 
 
 Reference has been already made to the irregular appearance of the 
 circumferential margin of the lens. The toothed-like arrangement of 
 
DISSECTIONS OF THE EYE FROM THE FRONT 39 
 
 the edge has been explained as evidence of the strain exercised on the 
 capsule by the tension of the fibres of the zonule. To this arrangement 
 there is one exception, viz. that of the foetal specimen (No. 32), where 
 the circumference of the lens exhibits quite an even edge, due probably 
 to the fact that it has not been subjected to the strain exercised on it 
 during accommodation. The greater degree of convexity of the-anterior 
 surface of the foetal lens has been already alluded to. 
 
 For other details concerning the lens see pp. 25, 45 and 49. 
 
CHAPTER III 
 
 ANTERIOR HALF OF THE EYE SEEN FROM BEHIND 
 
 THIS includes the series of photographs, Nos. 33 to 47, which exhibit 
 the arrangement of the structures within the anterior half of the eye as 
 seen from behind, the globe having been bisected in the equatorial 
 plane. 
 
 Externally, the coats of the eye are seen divided ; outside lies the 
 sclera, displaying an average thickness in this situation of 0-53 mm. 
 
 Not unfrequently the perichorioidal space is revealed by the separation 
 of the chorioid from the sclera, as in Nos. 33 and 34, the tissue which in- 
 tervenes between them being split into two lamina, of which the external, 
 the lamina fusca, adheres to the internal surface of the sclera, and imparts 
 to it its pigmented appearance, whilst the inner layer, the suprachorioidal 
 membrane, remains united to the external surface of the vascular 
 chorioid. The tissue which unites these two layers is permeated with 
 lymph spaces and traversed by the ciliary nerves and the long ciliary 
 arteries. 
 
 In No. 47 the sclera has been cleared of all the structures which lie 
 within it ; its inner surface is irregularly pigmented owing to the adher- 
 ence of the lamina fusca. In front its union with the cornea is seen, 
 and here a good demonstration is given of the groove (sulcus circularis 
 corneae) which lies immediately behind the internal sclero-corneal junction. 
 This groove, as has been explained (p. 16), is formed by the projection 
 of the circumference of the cornea internally and in front, whilst its 
 outer wall is formed externally and behind by the inner surface of the 
 sclera overlain by the pectinate ligament ; this, be it remembered, forms 
 the outer wall of the filtration angle of the anterior chamber. The pig- 
 mented inner surface of the sclera ends abruptly in front, just wide of 
 the circular sulcus, in a light-coloured well-defined edge ; it is from this 
 that the annular ligament, to which the ciliary muscle and the iris are 
 attached, has been removed in detaching the ciliary body, and it is along 
 this margin that the fibres of the pectinate ligament passing to the front 
 of the iris will have been torn across. The canal ofSMemm, which lies 
 immediately in front of the light zone which indicates the position of 
 the annular ligament, will, in all probability, have been laid open here 
 and there in the course of the dissection, but it is too minute to be seen 
 in the preparation. 
 
 For further details regarding the sclera see pp. 7 and 53. 
 
 Occupying the centre of the preparation (No. 47), the inner surface 
 
ANTERIOR HALF OF THE EYE SEEN FROM BEHIND 41 
 
 of the cornea is exposed. As has been stated, it bulges somewhat at its 
 circumference so as to take part in the formation of the groove which 
 surrounds its periphery. The bottom of the groove is angular and forms 
 a crisp furrow which on meridional section appears as a definite kink ; 
 this marks the position of the internal sclero-corneal junction, and it is 
 here, seen very clearly in the lower part of the preparation, where it 
 appears as a dark line, that Descemet's membrane, which covers the 
 inner surface of the cornea, abruptly alters its character, and breaks up 
 into the trabecular tissue of the pectinate ligament, the outer surface of 
 which is related to the externally placed sclera, the canal of Schlemm 
 intervening. The irregular appearance displayed by the inner surface 
 of the cornea is due to the wrinkling of Descemet's membrane under the 
 influence of the hardening reagent. 
 
 For further details relating to the cornea see p. 8. 
 
 The chorioid coat. In the majority of the preparations this layer 
 can be seen distinctly at the cut edge of the section as it lies between 
 the sclera externally and the pars optica retinae internally. In some 
 instances it is separated from the sclera by the opening up of the 
 perichorioidal space, in which condition it has overlying it externally the 
 sitprachorioidal membrane (see Nos. 33 and 34). In other of the pre- 
 parations it has separated from the nervous layer of the pars optica 
 retinae, as in Nos. 35 and 43 ; but here be it noted that its inner surface 
 is dark in colour owing to the fact that the pigment layer of the retina 
 is still adherent to it. The separation takes place, therefore, not between 
 the chorioid proper and the retina, but between the nervous and 
 pigmented layers of the retina, as has been fully explained on p. n. 
 Little more need here be said regarding the chorioid, as it has been 
 described at length in Chapter I (p. 10). 
 
 The anterior extension of the uvealcoat, as seen from within, may now 
 be considered, though it should be clearly understood that in front of the 
 ora serrata of the pars optica retinae it is overlain internally by the pars 
 ciliaris and pars iridica retinae, which impart to it its pigmented appear- 
 ance. In front of the ora serrata there is a fairly smooth circular 
 pigmented zone, about 3-6 mm. in width, exhibiting the appearance, when 
 the vitreous is in position, of faint radial striation (see Nos. 33 and 34). 
 This is the orbiculus ciliaris. After the removal of the vitreous this area 
 can be more readily examined ; it will then be obvious that the striation 
 is due to the disposition of the vessels which are here seen running 
 radially from the ciliary processes in front towards the ora serrata 
 behind. These are the veins of the ciliary processes which are passing 
 backwards to drain into the vorticose veins. As will be observed in No. 37, 
 some of the larger of the vessels arise from the ciliary processes, others 
 appear to begin in the valleys between them. In the same preparation, 
 and also in No. 36, some of the fibres of the zonule of Zinn are seen to 
 
42 ANTERIOR HALF OF THE EYE 
 
 arise from the tissue overlying the fore part of the orbiculus, immediately 
 behind the inspring of the ciliary processes : these appear as tense 
 delicate glistening strands which require careful focusing and good 
 light to show them. 
 
 Within the orbiculus lies the corona ciliaris, composed of the ciliary 
 processes, which vary in number from 67 to 84. They impart a goffered 
 appearance to this part of the ciliary body, and stretch forwards and 
 inwards towards the circumference of the lens, from which, however, 
 they are separated by the circumlental space. These processes measure 
 on an average 2 mm. long, about 0-5 mm. wide, and rise i mm. from 
 the surface. 
 
 In Nos. 33, 34, 35, 36 and 37, the circumlental space appears as a dark 
 ring immediately surrounding the lens, and careful examination in the 
 stereoscope reveals the presence of faint radial striae crossing it : these 
 are the fibres of the zonule of Zinn. A better view of the circumlental 
 space is obtained when the cornea and iris have been completely removed 
 from the front of the eye; then, if the preparation be viewed by 
 a combination of reflected and transmitted light, the circumlental space 
 appears as a light ring around the lens, whilst the rounded anterior 
 extremities of the ciliary processes as well as the fibres of the zonule 
 are better displayed (see Nos. 39, 40 and 41). 
 
 The ciliary processes consist of upstanding folds containing a number 
 of tortuous vessels in their interior ; each fold is laterally compressed, 
 and the free edge of the fold, thick and rounded, rises gradually from 
 the fore part of the orbiculus, and, gently curving inwards, ends abruptly 
 by a rounded extremity which projects into the posterior camera of the 
 aqueous chamber immediately behind the ciliary attachment of the iris. 
 These folds, to the number of 70 or 80, are placed side by side in radial 
 fashion, so that there are a corresponding series of interspaces or valleys 
 between them. 
 
 In their appearance and arrangement they display considerable 
 differences. In some the free edges of the folds are fairly straight and 
 regular (No. 34); in others (Nos. 39 and 40) they are irregular and 
 tortuous. On the other hand, it is not uncommon to meet with an 
 arrangement such as that exhibited in No. 43, in which, between each 
 pair of processes (which in this case number about 68), there are 
 subsidiary folds occupying the valleys; these are not so large as the 
 major processes, but, though smaller, are fairly prominent and well 
 defined. These have been named the ciliary folds to distinguish them 
 from the ciliary processes. 
 
 When the lens is in situ the fibres of the zonule of Zinn pass from 
 it across the circumlental space to the region of the corona ciliaris. In 
 several preparations (Nos. 37, 39 and 40), the arrangement of these fibres 
 and their relation to the ciliary processes are well displayed. As has 
 
SEEN FROM BEHIND 43 
 
 been said, some of the fibres spring from the fore part of the orbiculus 
 behind the position of the ciliary processes, but the majority arise from 
 the ciliary body in the region of the corona. An inspection of Nos. 37 
 and 39 clearly demonstrates how this takes place : the fibres take their 
 origin from the surface of the ciliary body in the intervals or valleys 
 between the ciliary processes, and not from the processes themselves. 
 As several fibres appear to spring from each valley, this accounts for 
 the appearance displayed by the zonule as if the fibres were grouped 
 in bundles. 
 
 A further dissection, which entails the removal of the lens and the 
 division of the suspensory ligament, completely exposes the ciliary 
 processes and exhibits the relation of the corona to the back of the iris. 
 This has been done in Nos. 43, 44, 45 and 46. In Nos. 44 and 45 the 
 darker colour of the back of the iris contrasts with the lighter tint 
 of the corona. The preparation, of which No. 46 is a photograph, has 
 been subjected to the bleaching action of peroxide of hydrogen, which, 
 curiously enough, although it has extracted all the pigment from the 
 region of the corona, does not materially seem to have affected the 
 uvea of the iris. In No. 46 the ciliary processes are beautifully shown. 
 Their summits are devoid of pigment : this is not an uncommon appear- 
 ance, and cannot be explained on the supposition that the removal of the 
 vitreous and hyaloid membrane has entailed the loss of such an amount 
 of pigment as may have adhered to them, for the same unpigmented 
 condition along the summits of the processes may be seen in specimens 
 where the vitreous has not been taken away (No. 33). In No. 46 the 
 processes clearly display their vascular structure by the tortuosity 
 which they exhibit on their surfaces ; this is well shown on the right 
 side of the preparation, where, emerging from the root of each process, 
 may be seen a vessel of considerable size passing backwards into the 
 orbiculus. The preparation also shows that the tissue underlying the 
 valleys between the processes is likewise beset with tortuous vessels, as 
 the irregularities on the overlying surface prove. A certain amount of 
 fluffy tissue may be seen floating in the fluid overlying the processes 
 (the preparations were photographed under fluid) : this is the remains of 
 the zonule, whilst here and there a stray fibre is seen, indicating the 
 nature of that structure. 
 
 In No. 44, a similar view, the anterior extremities of the ciliary 
 processes exhibit what seems to be a deflection of the process to one or 
 other side, imparting to it a club-shaped appearance. In the bleached 
 preparation (No. 46), the processes themselves along their free edge are 
 fairly even and regular, but on their sides and in the valleys between, 
 down which the ciliary folds may be traced, they present anteriorly 
 a pitted and honeycombed appearance, as may be well seen on the right 
 side of the preparation. These are doubtless the openings of the ciliary 
 
44 ANTERIOR HALF OF THE EYE 
 
 glands of Collins ; and be it noted that their position, lying in front, as 
 they must do, of the hyaloid membrane of the vitreous, will direct their 
 secretions into the posterior camera of the aqueous chamber. At the 
 lower part of the preparation a few scattered fibres of the zonule 
 are seen arising from the valleys. 
 
 For further details concerning the ciliary processes, see p. 12. 
 
 In front of the anterior extremities of the ciliary process, but at some 
 little distance from their free ends, as indicated by the shadows they 
 cast (see the right side of the photograph No. 46), the posterior fluted 
 surface of the iris can be seen : this has been already described (see p. 35). 
 In the foetal eye at term (No. 38), the ciliary processes are somewhat 
 more club-shaped and not so compressed ; their anterior extremities 
 lie closer to the lens so that the circumlental space is narrower than 
 in the adult. In No. 42, from the eye of an eighth-month foetus, the 
 ciliary processes are shown in shadow and the circumlental zone 
 appears as a light ring around the lens, the cornea and iris having been 
 removed and a certain amount of reflected light having been used in 
 taking the photograph. The ciliary processes appear square at their 
 ends and more irregular in form. 
 
 The Retina. The internal coat is best seen in those preparations 
 (Nos. 33 and 34) where the vitreous is still in situ, the inner or nervous 
 layer of the pars optica is seen as a pale-grey translucent layer lining 
 the inner surface of the globe as far forwards as the ora serrata. This 
 margin, owing to the structures being viewed in perspective, is not so 
 well displayed as in the meridional sections, since the swelling of its 
 edge, due to the oedematous condition induced by the hardening 
 reagents or post-mortem changes, obscures the margin which marks 
 the definite transition of the pars optica to the pars ciliaris. In each 
 of the photographs, however, on the left side, the crenated border 
 of the ora serrata may be seen, and from the summits of some of the 
 spine-like processes a light-coloured slender thread may be observed 
 passing radially over the surface of the orbiculus (see also No. 43). 
 In the preparations where the vitreous has been removed these 
 appearances are not well shown, since a certain amount of the vitreous, 
 together with its hyaloid membrane, has remained attached to the 
 inner surface of the retina. In all the preparations, however, at the 
 cut edge of the section the retina is exhibited in such a way as to 
 demonstrate its division into two layers. This is perhaps best dis- 
 played in No. 43, where the vitreous no longer supports the inner 
 layer in position ; and here that layer, which is entirely constituted 
 of nervous elements, is shown separated from the dark pigmented 
 layer which lies external to it, and which has remained adherent to the 
 inner surface of the chorioid. The same may be seen in lesser degree 
 in Nos. 33 and 34, where the separation of the two layers is, at points 
 
SEEN FROM BEHIND 45 
 
 around the circumference, indicated by a dark line. In these prepara- 
 tions the nervous tunic will be seen to equal double the thickness of 
 the surrounding chorioid. 
 
 In the foetal eye at full term, represented in No. 38, the nervous 
 layer of the retina is seen to be proportionately and absolutely thicker 
 than in the adult; its appearance suggests that it is not -so -tightly 
 stretched over the inner surface of the globe, and it exhibits a velvety 
 look, as if looser and less compact in texture. Its anterior edge, 
 which is swollen and rounded, reaches nearer the coronary zone, 
 thus involving a narrowing of the orbicular zone. In this preparation 
 the vessels of the retina embedded within its inner surface are beautifully 
 displayed. It is not easy to distinguish between the arteries and the 
 veins, but it is quite evident that at this stage of development there is 
 a free anastomosis between these vascular channels, as may be seen 
 especially along the edge of the ora serrata, where these anastomoses 
 form a series of vascular arcades. This detail is of some interest, as 
 direct anastomosis between arteries or veins has been denied in the 
 case of the adult : possibly by the stretching of the retina to accom- 
 modate itself to the increased area of the growing globe these 
 connecting channels have disappeared. Noteworthy, too, is the fact 
 that the swollen edge of the ora is almost free from vessels. In the 
 eye of the eighth-month foetus the redundancy of the nervous layer 
 of the retina is very obvious. It is difficult to imagine that this infolding 
 of the nervous stratum is due either to post-mortem changes or the 
 influence of hardening reagents ; it seems more reasonable to suppose 
 that it is a provision whereby it may accommodate itself to the growth 
 of the globe. Its thickness, too, is remarkable, and it is seen to extend 
 well forwards towards the ciliary processes ; only a few vessels are 
 seen coursing through its internal layers. 
 
 The anterior extension of the retina over the surface of the orbiculus 
 ciliaris and ciliary processes has been already referred to (p. 24). Nothing 
 further need be said than that, by its pigment layer, the pars ciliaris 
 retinae imparts the coloured appearance to the structures which it 
 overlies. It will, however, be noticed, in such preparations as Nos. 43, 
 44, 45 and 46, in which the lens has been removed, that the further 
 extension of the retina (pars iridica retinae) on to the posterior surface of 
 the iris exhibits a greater depth of colour, as here not only its pigment 
 layer but the cells which lie within it are loaded with colouring 
 matter, constituting what is sometimes called the uvea of the iris. 
 
 For further details concerning the retina see pp. 25 and 56. 
 
 The Lens. The lens, as seen in situ from behind, exhibits 
 different appearances according to the nature of the light. In Nos. 39 
 and 40, both from the same preparation, the lens star consists of a stellate 
 arrangement of the lamellae of which the lens is composed, with nine 
 
46 ANTERIOR HALF OF THE EYE 
 
 or ten processes radiating from the centre and gradually tapering until 
 they reach the circumference ; the angular intervals between these 
 spokes are occupied by folded lamellae arranged like the sides of a 
 Gothic arch ; the summits of the arches, or the folded edges of the 
 lamellae, being directed towards the angles formed by the spokes. 
 In No. 35 the lamellar arrangement is not so well shown ; here the 
 star consists of a rosette-like arrangement, having ten lanceolate petals ; 
 there are also indications of lines of cleavage near the centre on the 
 right-hand side. In No. 33 there are faint indications of a radial 
 striation, and in No. 34 there are ten or eleven lighter lines all con- 
 verging towards the centre, while, close to the circumference, small 
 wedge-shaped dark masses lie between these lines. The other pre- 
 parations only faintly disclose any appearance of structure. 
 
 On p. 27 the greater convexity of the central part of the posterior 
 surface of the lens, as seen in meridional section, was referred to. 
 The same appearance can be made out stereoscopically in the view of 
 its posterior surface, as displayed in Nos. 33, 34 and 41 ; the incidence 
 of the lighting in each case reveals the fact that the central portion of the 
 lens rises with a more pronounced degree of convexity from the flatter 
 and less convex peripheral portion. The circumference of the lens in 
 most cases displays that irregularity of outline to which attention has 
 been already directed (p. 37). Hereto the fibres of the zonule of Zinn 
 are attached, but in Nos. 39 and 40 the equator of the lens is seen to 
 correspond to a flattened zone between two borders, as has been 
 already described. In both these photographs the double borders are 
 seen, each receiving its quota of fibres from the zonule, the space 
 between the two strata of fibres corresponding to the so-called canal of 
 Petit, the inner side of which is formed by the circumference of the lens 
 lying between the two borders, the surface to which the name equatorial 
 zone has been applied. Another feature, to which attention should be 
 directed, is illustrated in No. 41, wherein a delicate membrane is seen, 
 here and there raised from the circumference of the lens by the traction 
 of the fibres of the zonule. This appears to confirm the observations 
 of Retzius, and demonstrates the existence of a pericapsular membrane, 
 to the dragging out of which by the fibres of the zonule Retzius 
 attributes the toothed and irregular outline of the circumference of the 
 lens. In the foetal eye at birth, shown in photograph No. 38, the cir- 
 cumference of the lens is even and regular. The posterior surface 
 appears as if puckered in the centre by a four-rayed cleft, the limbs of 
 which spread and branch irregularly into the surrounding tissue. 
 Curiously enough, the appearance presented by the photograph of an 
 eighth-month foetus (No. 42) exhibits the posterior surface of the lens 
 full, rounded, and structureless, and without any evidence of the con- 
 dition displayed in No. 38. Possibly the appearance exhibited in the latter 
 
SEEN FROM BEHIND 47 
 
 is due either to post-mortem changes or to some error in development. 
 In the eighth-month eye the circumference of the lens is quite regular 
 and without any evidence of the attachment of the fibres of the zonule. 
 
 For further details concerning the lens see pp. 29, 38 and 50. 
 
 The circumlental space, which measures on an average i mm. 
 in breadth, is seen from behind, under different conditions of light. 
 By reflected light, with the fore part of the eye intact, it appears as 
 a dark ring around the lens. When viewed by a combination of trans- 
 mitted and reflected light, the cornea and iris having been removed, it 
 shows up as a light annular zone. Under the latter conditions the 
 fibres of the zonule which cross it are better displayed, since they stand 
 out as dark strands against a light ground. In this fashion they are 
 displayed in Nos. 39, 40 and 41. Externally, the circumlental space is 
 bounded by the goffered surface of the corona radiata, for be it remem- 
 bered that the rounded extremities of the ciliary processes project 
 somewhat in front of the equatorial plane of the lens ; so that the widest 
 part of the interval between the lens and the ciliary processes will lie 
 slightly behind their anterior rounded extremities. The inner limit of 
 the space coincides with the equator of the lens ; but since, as we have 
 seen, this is not always a linear surface but often a more or less 
 flattened border, it is better to describe its inner margin as corre- 
 sponding to the equatorial zone of the lens, viz. that surface around the 
 circumference which lies between the attachment of the two strata of 
 the fibres of the suspensory ligament. 
 
 The zonule of Zinn, or the suspensory ligament of the lens. The 
 fibres which constitute this structure, as seen from behind, are best 
 displayed in No. 40, where they appear as dark strands against a light 
 ground ; the cornea and iris having been removed, a certain amount of 
 reflected light passes through the circumlental space and thus renders 
 more apparent any structures which cross it. In this preparation, in 
 which the vitreous has been removed, the fibres of the zonule display 
 the appearance of being grouped in bundles, with interspaces between, 
 in which the fibres are not so closely packed together. This arrange- 
 ment is doubtless due to the fact that the majority of the fibres arise 
 from the corona radiata in the valleys between the ciliary processes, 
 where they may be seen springing from the bottom and sides of these 
 recesses in different equatorial planes. It may be well to point out in 
 this connexion that some of the fibres arise not from the valleys but 
 from the fore part of the orbiculus immediately behind the attachment 
 of the ciliary processes, as may be seen in Nos. 36 and 37, where their 
 connexion with the orbiculus lies in line with the position of the 
 valleys. From a study of photograph No. 40 in the stereoscope it will 
 be evident, particularly in the upper part of the preparation, that, in the 
 main, these fibres are disposed in two strata, which are attached 
 
48 ANTERIOR HALF OF THE EYE 
 
 respectively to the two borders which include between them the 
 equatorial zone around the circumference of the lens. It is not dis- 
 puted that other of the fibres may be attached at intermediate points 
 along this zone, but the majority of the fibres appear to have the attach- 
 ments indicated. The interval between these two strata corresponds 
 to the so-called canal of Petit, which surrounds the lens and in part 
 corresponds to the circumlental space, though it would appear that 
 this interval has extensions which pass outwards between the fibres as 
 they occupy the valleys between the ciliary processes. In the right- 
 hand lower side of this region, in No. 40, the fibres of the posterior 
 stratum have been torn away in removing the vitreous and its hyaloid 
 membrane, thus proving the intimate connexion which exists between 
 these layers. Here the attachment of these fibres to the posterior 
 border of the equatorial zone is clearly demonstrated, as they are turned 
 towards the spectator. 
 
 The fibres of the zonule are clearly seen in the eighth-month 
 foetal eye (No. 42) ; their arrangement requires no further description, 
 except to point out that there are no irregularities around the circum- 
 ference of the lens to indicate their attachment to that structure. 
 
 For further details concerning the suspensory ligament see pp. 29, 
 37 and 50. 
 
 The Vitreous. Little need be said about this, as owing to its trans- 
 parent nature but slight evidence of its structure can be made out. It 
 is seen in situ in Nos. 33 and 34, where a faint cloudiness of its tissue 
 indicates its presence. In these preparations it serves to keep in 
 position the structures which surround it, and its external hyaloid mem- 
 brane is everywhere applied to the inner surface of the retina. In most 
 of the other preparations of this series it has been, in whole or in part, 
 removed ; under the latter conditions, the structure of the hyaloid 
 membrane, with some of the vitreous tissue still clinging to it, is seen 
 overlying the retina (see Nos. 35, 36, 37 and 40), the surface of which 
 is thereby obscured. In No. 37 the hyaloid membrane overlies the 
 orbiculus, where its presence is demonstrated by a tear in it, visible in 
 the left-hand lower corner of the preparation ; through the torn portion 
 the pigmented surface of the orbiculus is more clearly displayed. In 
 the zonular region its presence is indicated by the filmy appearance 
 represented in No. 36, and its intimate connexion with the posterior 
 fibres of the zonule is exhibited in No. 40 (right-hand lower side), 
 where, in attempting to remove it, some of these fibres have been torn 
 away from their ciliary attachment. 
 
 In the foetal eyes, Nos. 38 and 42, the vitreous is still in situ; in neither 
 is there any indication of the remains of a hyaloid canal. In No. 42 
 a delicate smoky look indicates some appearance of structure. 
 
 For further details concerning the vitreous see pp. 30 and 61. 
 
CHAPTER IV 
 
 LENS 
 
 THIS series includes a number of preparations (Nos. 48 to 57) 
 designed to exhibit more clearly the connexion of the lens with its 
 suspensory ligament. 
 
 The specimens in some instances have been subjected to the 
 influence of staining reagents, so as to render more obvious the differen- 
 tiation of the tissues. No. 48 is a photograph of the anterior surface of 
 the lens, lying in the patellar fossa of the vitreous. The preparation was 
 made, after the ciliary body had been removed, by snipping through 
 the hyaloid membrane at some distance from the circumference of the 
 lens; the tissue of the vitreous was then carefully brushed away, 
 leaving the hyaloid membrane intact ; the specimen was then stained in 
 picro-nigrosin. An inspection of the photograph in the stereoscope 
 shows the lens lying in front of the stained hyaloid membrane, the 
 anterior surface of which in the upper part of the photograph exhibits 
 a goffering around the peripheral cut edge in correspondence with the 
 ciliary processes, which have been taken away from its surface. The 
 folding of the membrane, as here displayed, is not so deep as to 
 suggest that it follows accurately the contours of the surface of the 
 corona, but rather that it dips down only slightly into the valleys and 
 bridges across the interval between the processes, thus leaving a space 
 in front between the floor of the valley and the external surface of the 
 membrane. In this way are formed the recesses of Kuhnt, which are 
 in communication anteriorly with the posterior camera of the aqueous 
 chamber, and into which (see p. 44) the ciliary glands of Collins dis- 
 charge their secretion. These recesses are, of course, traversed by 
 some of the fibres of the zonule. Lying in front of the hyaloid mem- 
 brane and quite distinct from it are seen the fibres of the suspensory 
 ligament. These are no longer stretched, since their connexions with 
 the ciliary body have been torn away, but their attachment to the lens 
 capsule is clearly shown, and, with a little care, will be distinctly seen 
 to be disposed in two more or less definite strata where they join the 
 lens, both quite distinct from the hyaloid membrane, which lies behind. 
 No. 49 is a posterior view of the same preparation ; in this position the 
 hyaloid membrane lies in front of the lens, and its inner or posterior 
 surface is seen to be irregular and ragged where the trabecular exten- 
 sions from it into the substance of the vitreous have been torn across. 
 A point of particular interest, in this specimen, is that it clearly demon- 
 
5 o LENS 
 
 strates the existence of the hyaloid membrane over the surface of the 
 patellar fossa, since, as may be seen in the photograph, there is a tear 
 in it across its centre, through which the lens is clearly visible. This 
 detail will be further referred to presently. On the hyaloid membrane 
 the impress of the ciliary processes is seen, and if carefully inspected 
 in the stereoscope the fibres of the zonule can, in places, be observed 
 through the hyaloid membrane. This is rendered difficult by the amount 
 of loose tissue attached to the posterior surface of the hyaloid, but in 
 the lower left-hand corner of the photograph the suspensory fibres are 
 clearly visible lying on the farther side of the membrane. 
 
 In No. 50 the same preparation has been subjected to a further dis- 
 section. The photograph, like the last, is a view of the posterior 
 surface of the specimen ; but here one half of the hyaloid membrane has 
 been removed, and as the membrane has overlain the back of the lens 
 it has been stripped off from the posterior surface of the capsule. This 
 convincingly proves that this layer is continuous over the surface of the 
 patellar fossa, since on the left side it is still seen in greater part over- 
 lying the lens, and although the continuity of the peripheral part of the 
 membrane and that which covers the posterior surface of the lens has 
 been interrupted in places by a tear, yet if the upper torn vertical edge 
 of the membrane be examined carefully it can with certainty be traced 
 on to and over the posterior surface of the lens. The connexion of this 
 layer with the posterior surface of the capsule must be fairly intimate, 
 as proved by the manner in which it has been torn away from the lens 
 on the right side, since the part which remains on the left side displays 
 no free or independent edge, but is apparently evenly united to the 
 posterior lens capsule. But the removal of the right half of the hyaloid 
 membrane, as will be seen, has not carried with it the zonular fibres, for 
 these are free and independent of the hyaloid membrane and still remain 
 attached to the lens, where on the right and lower side their arrange- 
 ment into two more or less distinct strata is clearly seen. It thus 
 appears that the fibres of the zonule must be regarded as structures 
 distinct and apart from the hyaloid membrane, though there can be no 
 doubt that the relation between them must be very intimate, especially 
 at their peripheral part, and particularly in the case of the fibres which 
 form the posterior stratum of the zonule. In Nos. 51 and 52 the lens and 
 lens capsule have been removed with the fibres of the zonule still 
 adherent, care having been taken to strip the latter off the corona 
 ciliaris as far back as possible. No stain has been employed, so that if 
 the hyaloid membrane, or parts of it, are still adherent to the preparation, 
 these owing to their transparency do not show ; but care was taken as 
 far as possible to remove the hyaloid, and that this has been successful 
 is suggested by the somewhat fluffy appearance of the posterior surface 
 of the lens as exhibited in the lower specimen in No. 52. The point of 
 
LENS 51 
 
 interest, for the display of which these preparations have been intro- 
 duced, is this, that whilst for the space of about 1-5 mm. from the cir- 
 cumference of the lens the fibres of the zonule appear independent and 
 separate, yet when they are traced further outwards they become con- 
 fluent, so as to form a thin and delicate membrane, which, from its 
 disposition, must have been torn away from the surface of the pars 
 ciliaris retinae, and which in its relation thereto must have lain between 
 that layer and the hyaloid membrane internally. It thus appears that 
 we must regard the fibres of the zonule, or suspensory ligament \ as formed 
 by the shredding of a delicate membrane blended posteriorly with the 
 layers of the pars ciliaris retinae as it overlies the forepart of the orbi- 
 culus and the furrows between the ciliary processes. As has been shown, 
 these fibres of the zonule, having a common origin, as they pass to the 
 circumference of the lens tend to arrange themselves into two layers, 
 each attached respectively to the anterior and posterior borders of the 
 equatorial zone of the lens. A few, doubtless, occupy an intermediate 
 position, whilst the interval between the two strata corresponds to the 
 canal of Petit. 
 
 The common origin of the fibres from the membranous layers 
 described is shown also in No. 53, and in this preparation their sepa- 
 ration into two layers, as suggested, is also fairly clearly shown in the 
 stereoscope. 
 
 In those preparations in which the zonule has been separated from 
 its peripheral attachment, although the connexion of its fibres with the 
 circumference of the capsule of the lens is clearly seen owing to their 
 now relaxed condition, the points of attachment to the capsule do not 
 exhibit the same evidence of strain as when the parts are examined in 
 situ, with all the connexions of the zonule complete. 
 
 Nos. 54 and 55 have been introduced because in these specimens 
 the corona ciliaris has been separated from its scleral attachments, and 
 in consequence, having lost that fixity of position which is their normal 
 condition, the fibres of the zonule, as revealed by transmitted light, 
 crossing the circumlental space are no longer represented in a tense 
 and stretched condition, but appear in places somewhat loose and 
 relaxed. 
 
 No. 56 has been added to the series because it exhibits an unusual 
 arrangement in the appearance of the zonule. In this preparation, as 
 seen on the right side and also in the lower left-hand corner of the 
 photograph, there are some delicate fibres having a concentric arrange- 
 ment. These appear to lie between the two strata of the zonule, and con- 
 sequently within or around the canal of Petit. Their nature is not clear ; 
 possibly they may be due to the presence of a fine endothelial lining, 
 partial or complete, to that space. 
 
 No. 57 is a view of the lens with its associated parts from a 6i-months' 
 
 D 2 
 
52 LENS 
 
 foetus. The lens, which more nearly approaches the spherical form 
 than in the adult, is surrounded at its equator by a collar consisting of 
 the corona ciliaris internally and that part of the retina which ultimately 
 forms the ora serrata externally. The vitreous enclosed in its hyaloid 
 membrane is still in position, and exhibits within its substance what is 
 the particular feature of interest in this preparation, viz. the hyaloid 
 artery, passing forwards to the posterior surface of the lens, where it may 
 be seen breaking up into a number of branches. 
 
 For further details regarding the lens and the zonule of Zinn see 
 pp. 29, 37 and 47. 
 
CHAPTER V 
 
 POSTERIOR HALF OF THE EYE 
 
 THIS includes Nos. 58 to 67 of the series of photographs. These are 
 taken from preparations designed to show the contents of the posterior 
 half of the globe, the eyeball having been divided equatorially. Some 
 other specimens are also introduced to exhibit the structure of the uveal 
 tract. 
 
 In Nos. 58, 59, 60, 62 and 63 the circumference of the section displays 
 the coats of the eye divided. Externally the cut edge of the sclera 
 is seen, within which lies the chorioid. In only one preparation, No. 62, 
 is this latter seen separated from the sclera. The narrow cleft thus 
 exposed is visible in the upper and right part of the preparation, 
 and corresponds to the position of the perichorioidal lymph space, and 
 is formed by the splitting of the tissue which unites the sclera and 
 chorioid into two layers the lamina fusca, which adheres to the inner 
 side of the sclera, and the suprachorioidal membrane which remains 
 connected with the external surface of the chorioid. It is along this 
 line of cleavage that the contents of the globe have been removed from 
 the inner surface of the sclera in the preparation of which No. 64 
 is the photograph. In the view of the inner aspect of the scleral coat 
 thus exposed, the pigment adherent to its inner surface is that deposited 
 within the lamina fusca. Near the centre of the preparation, on the 
 summit of a slight elevation, as displayed in this specimen, is the inner 
 opening of the scleral optic foramen (foramen opticum sclerae). The 
 width of this opening measures on an average 2 mm. ; around its 
 circumference is seen a narrow ring of adherent pigment. The white 
 area within it corresponds to the divided optic fibres, which have been 
 rendered opaque by the action of the hardening reagents, thus obscuring 
 any view of the lamina cribrosa which in the unfixed condition would 
 probably be seen. In the centre of the divided nerve three little dark 
 spots are visible. These are vessels ; the smaller and darker of the 
 points is probably the arteria centralis retinae, whilst the fainter and 
 slightly larger spots mark the position of the companion veins, which 
 have probably not yet united. At a distance of two or three millimetres 
 from the circumference of the scleral optic foramen there is a zone 
 in which appear a number of light strands with a double outline. Some 
 of these are definite structures, but others seem to be the unpigmented 
 paths in the substance of the lamina fusca, which mark the position of 
 
54 POSTERIOR HALF OF THE EYE 
 
 the vessels and nerves which here pierce the sclera ; some of these are 
 undoubtedly vessels and correspond to the posterior ciliary arteries 
 which, after passing forward for some little distance in the perichorioidal 
 space, enter the substance of the vascular chorioidal layer. Others 
 of a larger size, of which over twenty can be counted, take a meridional 
 course towards the cut edge of the section, and are either the ciliary 
 nerves themselves or the paths which indicate their position. In 
 the upper part of the preparation, corresponding to a line passing north 
 and south in the compass, an artery of some length is seen : it is not 
 unlikely that this is one of the long posterior ciliary arteries which has 
 been torn across in part of its course through the perichorioidal space. 
 At the bottom of the photograph, a little to the right of south, is what 
 seems to be one of the vorticose veins piercing the sclera. In the part 
 of the preparation which is in shadow (the right side of the photograph), 
 there are appearances in the distribution of the pigment which suggest 
 the arrangement of the radicles of the vorticose veins of the chorioidal 
 layer which lies immediately internal to this exposed surface of the 
 sclera. 
 
 Further details referring to the sclera may be found on pp. 7 and 40. 
 
 In Nos. 58, 59, 60 and 62, the next layer, divided at the edge of the 
 section, immediately internal to the sclera, is the chorioid. In the 
 majority of instances it is represented as in contact with the sclera, 
 the intervening layer, as has been stated, consisting of the lamina fusca 
 and lamina suprachorioidalis. These have a tendency to separate, as 
 has been explained ; under normal conditions, however, there is only 
 an irregular lymph space between, through which pass the ciliary 
 nerves and the long posterior ciliary arteries on their way to the 
 ciliary region anteriorly. Across this space posteriorly the posterior 
 ciliary arteries take a course to enter the chorioid layer, whilst in the 
 region of the equator the large vorticose veins, usually four in number, 
 traverse it so as to enter the substance of the sclera, through which they 
 pass very obliquely in a backward direction. These veins are usually 
 arranged in an upper and lower pair, their points of emergence through 
 the sclera being about 90 apart. 
 
 Nos. 58, 59 and 62 show the chorioid separated from the nervous 
 layer of the pars optica retinae. The pigmented appearance on the inner 
 surface of the chorioid, thus exposed, is due, as has been previously 
 explained (see p. 19), to the adherence to it of the pigment layer of the 
 retina. In No. 67 the whole of the outer surface of the uveal tract has 
 been exposed by the removal of the sclera and cornea from its outer 
 surface. This aspect of the structure is covered with the non-vascular 
 suprachorioidal membrane, formed, as has been elsewhere described, by 
 the splitting of the tissue which unites it externally with the sclera. The 
 line of cleavage has taken place through the irregular lymph space 
 
POSTERIOR HALF OF THE EYE 55 
 
 called the perichorioidal space, which lies between the sclera externally 
 and the chorioid internally. In this space thus laid open by the 
 removal of the sclera, the vessels and nerves which traverse the loose 
 connective tissue within it on their way to the ciliary zone anteriorly are 
 now displayed. These are the ciliary nerves, of which eight or nine can 
 be seen passing forwards to break up anteriorly into branches which 
 unite to form the ciliary plexus (plexus gangliosus ciliaris) on the outer 
 exposed surface of the ciliary region, where they lie external to the 
 orbicularis ciliaris and ciliary muscle, as may be seen in the upper part of 
 the preparation. Accompanying one of these nerves, near the left side 
 of the photograph, a long slender vessel is seen. This is one of the long 
 posterior ciliary arteries passing forwards to the fore part of the ciliary 
 zone to form with its fellow of the opposite side, together with the 
 branches of the anterior ciliary arteries, the arterial circle placed within 
 the substance of the ciliary attachment of the iris. This arterial ring is 
 known as the circulus iridis major. 
 
 The outer surface of the uveal tract exhibits a division into zones in 
 correspondence with the differentiation in structure displayed by its 
 inner surface. Thus, anteriorly (seen in the upper part of the photo- 
 graph) there is a lighter coloured zone, which corresponds to and is 
 formed by the outer surface of the ciliary muscle. Behind this is 
 a more deeply tinted zone, limited posteriorly by a lighter ring with 
 less pigment. This latter corresponds to the position, within, of the 
 ora serrata, and the surface lying between this and the zone of the 
 ciliary muscle in front overlies and harmonizes with the orbiculus ciliaris 
 as seen from the inner side. At the lighter ring, corresponding to the 
 attachment of the ora serrata, the parallel arrangement of the veins 
 which drain into the vorticose veins is well displayed. Behind the 
 attachment of the ora serrata that portion of the outer surface of the 
 uveal tract which constitutes the chorioid is exposed. Internally, this 
 is overlain by the pars optica retinae. Externally, the colour which it 
 exhibits is largely due to the presence, internal to it, of the pigment 
 layer of the retina ; but here the converging radicles of the vorticose 
 veins are well displayed as light tracts directed towards a centre from 
 which one of the vorticose veins arises a large vessel which, traversing 
 the suprachorioidal space, escapes through the capsule of the globe by 
 piercing the sclera obliquely in the manner already described. The 
 layer of the chorioid occupied by the larger vessels, of which these 
 veins are the more superficial in this view, constitutes its vascular 
 lamina, and as thus exposed is merely covered by the lamina supra- 
 chorioidalis. Within the vascular layer, and separating it from the pig- 
 ment layer of the retina, is the chorio-capillary layer, of which no 
 distinct evidence is visible in the photograph. 
 
 No. 67 exhibits a view of the inner surface of the uveal tract, except 
 
56 POSTERIOR HALF OF THE EYE 
 
 the iris, which has been removed. Throughout nearly its entire extent 
 it is covered by the pigment layer of the retina. Along a line which 
 corresponds to the position of the ora serrata of the pars optica retinae, 
 and also for some distance in front of it, corresponding to the surface 
 of the orbiculus ciliaris, this pigment layer has been in part stripped off, 
 suggesting a more intimate connexion in this region between the con- 
 stituent layers of the retina than appears to hold good elsewhere. 
 Anteriorly (above in the photograph), the ciliary processes are seen, 
 forming the corona ciliaris. In front, their connexion with the annular 
 ligament is displayed; from the latter, however, the iris has been 
 detached. The cut edge of the section in this region reveals the 
 form of the ciliary body here due to the shape and thickness of the 
 ciliary muscle. Behind the corona the orbicular zone is seen, limited 
 posteriorly by a somewhat lighter narrow zone which corresponds to 
 the position of the ora serrata. In the places where the pigment layer 
 of the retina has been stripped off from the orbiculus, the arrangement 
 of the small veins, which are here passing from the ciliary processes to 
 the tributaries of the venae vorticosae, is well shown. Where these lie 
 in the same meridian with the main trunks of the venae vorticosae 
 the vessels appear arranged in parallel lines, but wide of this 
 meridian they pass with varying degrees of obliquity to join the area 
 drained by the tributaries of the vorticose veins. Behind the line of 
 attachment of the ora serrata, the part of the uveal tract which con- 
 stitutes the chorioid is displayed ; it is here overlain, however, by the 
 pigment layer of the retinae, the nervous lamina of which has been 
 removed. This pigmented stratum appears as a flocular-looking layer 
 of varying thickness and intensity, due no doubt to the irregularity of 
 its removal or to the treatment to which the specimen has been sub- 
 sequently subjected. The fact that this layer and the subjacent chorio- 
 capillary layer overlie the vascular lamina of the chorioid, in which the 
 tributaries of the venae vorticosae are disposed, accounts for the more 
 obscure display of these vessels in this view, as compared with that 
 shown in the last preparation (No. 65). 
 
 In two or three places the pigment layer has been torn through, 
 and in one of the holes so produced (see the left-hand lower side of the 
 photograph) the much lighter clear structure of the chorioid is revealed. 
 The fainter view of the tributaries of one of the vorticose veins, seen 
 through the overlying layers above referred to, exhibits the same 
 arrangement as that displayed in No. 65. 
 
 For further reference to the details of the uveal tract and the pig- 
 ment layer of the retina see pp. 10, 25, 41. 
 
 In Nos. 58, 59, 60, 62 and 63 the fundus oculi has been exposed by 
 the removal of the anterior half of the globe of the eye. Unfortunately, 
 the orientation of the specimens, when being photographed, has not 
 
POSTERIOR HALF OF THE EYE 57 
 
 been such as to represent them in the normal living position, nor could 
 this defect be remedied by rotating the prints so as to display the parts 
 in their approximate position, since such would interfere with their 
 stereoscopic effect. In consequence, in the descriptions given of them, 
 the points of the compass are taken as a means of interpreting the 
 horizontal plane. Unfortunately, too, it is not always easy to deter- 
 mine the side to which the eye belongs. With these reservations the 
 description of the specimens may now be proceeded with. No. 58 
 exhibits the appearance of the fundus of an eye which was removed 
 some time after receipt of an injury. The specimen was cut and 
 photographed within twenty minutes of the operation, no hardening 
 or fixing agents being employed. The appearances displayed, though 
 there is some optic neuritis, are as near an approximation to the con- 
 ditions in the living eye as can reasonably be expected. The retina, 
 though dimmed and having to some extent lost its transparency, has 
 not yet acquired the semiopaque translucent look which is so charac- 
 teristic of hardened preparations. Nor has it become irregular in its 
 disposition, a condition which is associated with the appearance of 
 oedematous-looking folds and elevations, which are so constantly met 
 with in the ordinary museum preparations. In this preparation the 
 pars optica retinae appears evenly spread over the inner surface of the 
 globe, except at the edge of the section, where already a separation 
 of the nervous from the pigmented layer tends to make its appear- 
 ance. Within the cup formed by the posterior half of the globe 
 two spots may be readily recognized, separated by a distance from 
 centre to centre of about 4 mm., the one light in colour, the other dark. 
 The former is the optic disk or papilla, the latter the yellow spot or 
 macula lutea. In the photograph a line connecting the two points 
 corresponds to the direction of the compass SE. by E. To place the 
 preparation approximately in its correct position, this line should be 
 rotated until it points slightly south of east, that is to say until it nearly 
 falls into the horizontal plane. As so oriented the optic disk is situated 
 4 mm. to the medial or nasal side of the macula, whilst the latter, which 
 lies pretty nearly in the visual axis of the globe, is placed very slightly 
 below its horizontal meridian. 
 
 The optic papilla, placed, as has been already stated, about 4 mm. 
 to the nasal side of the axis of the globe, displays a disk-like appearance 
 with an average diameter of about 1-5 mm. The white colour of the 
 disk is due to the fact that the transparent retinal fibres reveal the 
 white tissue forming the lamina cribrosa, which plugs like a sieve the 
 foramen opticum sclerae, and beyond which the nerve fibres passing 
 through it become myelinated. In No. 58 the centre of the disk 
 appears as a clear white spot, around which there is a slightly darker 
 zone, which appears to slope outwards into the surrounding retinal 
 
58 POSTERIOR HALF OF THE EYE 
 
 tissue. This elevated surface forms the colliculus nervi optici, and is 
 due to the increased thickness produced by the convergence of the 
 retinal optic fibres as they enter the anterior opening of the foramen 
 opticum sclerae, the circumference of which is sometimes marked by 
 a pigmented ring which corresponds to the abrupt cessation of the 
 pigmented layer of the retina. This is distinctly seen in preparation 
 No. 59. In No. 58, there is an appearance of faint pale striation 
 radiating from the optic disk into the surrounding retina; this may 
 possibly be due to the reflection of light from fibres of the optic nerve 
 layer, or in this case may be evidence of pathological change. Not 
 unfrequently there is a shallow hollow within the disk; this is the 
 physiological cup or excavation. It is well seen in No. 60, where the 
 elevated rounded margin of the colliculus is seen to throw a deep 
 shadow across the nasal half of this centrally placed depression. In 
 this view of it, the excavation appears to have a more abrupt wall on 
 its nasal side than on its temporal aspect, in which situation it seems 
 to slope more gradually towards the edge of the colliculus. A dimpled 
 appearance of the optic papilla is also seen in No. 61. It is within the 
 disk that the retinal vessels enter and leave the globe. In their general 
 distribution throughout the retina the veins accompany the arteries, 
 the larger branches pass forwards in the nerve-fibre layer, close to the 
 lamina limitans interna, so that in the surface of the retina here exposed 
 they occupy a superficial position. The veins can usually be distin- 
 guished from the arteries by their greater diameter and their less 
 tortuous course. 
 
 Though individual variations are met with, the distribution of the 
 vessels seen in Nos. 60 and 62 is probably the most typical. The arteria 
 centralis retinae, as it lies within the optic nerve, divides at or before 
 its emergence through the anterior opening of the foramen opticum 
 sclerae, consequently, when it lies within the area of the optic disk, it 
 usually appears as two or three branches, of these an upper and lower 
 branch usually turn over the rounded edge of the colliculus to supply 
 the upper and lower segments of the retina; each primary branch 
 divides into a medial and lateral branch; which are distributed respec- 
 tively to the nasal and temporal areas of the upper and lower retinal 
 segments. Not unusually a medial horizontal branch passes over the 
 inner lip of the physiological excavation, in line with but away from 
 the position of the macula lutea. Toward the region of the macula 
 two secondary branches, derived from the upper and lower primary 
 branches, curve outwards so as to enclose an elliptical area within the 
 centre of which the macula is placed. This, which may be regarded as 
 the typical arrangement, is well represented in Nos. 60 and 62, and is 
 seen also, though not so clearly, in Nos. 58 and 59. The emergence of 
 the vessels through the tissue, which forms the lip of the physiological 
 
POSTERIOR HALF OF THE EYE 59 
 
 cup, is often represented by an abrupt bend on their course, as is to 
 some extent displayed in No. 61, but better seen in the foetal eye 
 No. 63. The veins which take a corresponding course need not be 
 further described ; they unite to form a trunk which accompanies the 
 arteria centralis retinae within the substance of the optic nerve. 
 
 The macula, or yellow spot, lying, as has been stated, nearly exactly 
 in the position of the posterior pole of the visual axis of the eye, is 
 seen in No. 61 as a slightly elevated oval area, from 1-6 to 2-0 mm. in 
 diameter. This appears in the photograph NNW. from the optic disk. 
 The two should, of course, lie nearly in the same horizontal plane. The 
 swollen appearance of the macula is, in this preparation, no doubt 
 a post-mortem change emphasized by the hardening reagent employed ; 
 but it exhibits very clearly the depression in the centre of the macular 
 area called the fovea centralis, the sides of which are formed by the 
 rapid reduction in the thickness of the constituent layers of the nervous 
 stratum of the pars optica retinae. The dark colour imparted to the 
 fovea, which reaches its greatest intensity in the centre of that spot, 
 is due to the retinal pigment layer shining through the rapidly thinning 
 layers of the nervous retina. In No. 58, the photograph of the fresh 
 unhardened eye, only the dark spot corresponding to the fovea is 
 displayed ; there is no evidence of the surrounding macular area, due 
 probably to the failure of the photographic plate employed to reproduce 
 the difference in colour by which that area is defined. As seen in both 
 these preparations, the fovea has a diameter of about 0-5 mm. 
 
 In No. 60, in which the macula and the optic disk happen to lie 
 more nearly in the horizontal plane, the fovea is again represented as 
 a dark spot surrounded by a light area displaying a somewhat puckered 
 appearance ; beyond this a darker zone again intervenes between 
 a lighter circular area placed externally. This latter exhibits a some- 
 what swollen look, and from it there passes, to the temporal side of the 
 optic disk, an elevated fold along the edges of which two vessels may 
 be seen. These appearances are described in detail, since they appear 
 to present a transition stage between the conditions already described 
 in Nos. 58 and 61 and those which are displayed in Nos. 59, 62 and 
 63. In these latter preparations the fundus of the eye is traversed by 
 an elevated irregular fold, extending from the optic disk internally to 
 the region of the macula externally, where it encloses the fovea, which 
 always remains as a distinct pit; from this it tails outwards into the 
 temporal segment of the retina, on the surface of which it is gradually 
 lost. With the specimen oriented approximately in its normal position 
 the fold lies nearly in the horizontal plane. This appearance, long 
 known as the plica centralis, is undoubtedly the product of a post- 
 mortem change, as may be seen by comparing photographs Nos. 58 
 and 59, both taken from the same eye, the former in the fresh condition, 
 
6o POSTERIOR HALF OF THE EYE 
 
 the latter after it has been subjected to the influence of a harden- 
 ing reagent ; but here the fold is not represented in its characteristic 
 form, no doubt due to the fact that sufficient time was not allowed to 
 elapse before the specimen was put into the hardening fluid for the 
 post-mortem changes to exercise their influence. 
 
 In No. 62 the fold which lies SSE., instead of horizontally as it 
 should, is represented in what may be termed its typical form. In 
 numerous preparations in my collection the shape and disposition of 
 this fold are so remarkably alike, as may be seen by comparing No. 62 
 with that of the foetal eye No. 63, that one is forced to the conclusion 
 that the configuration of the fold is due to some structural difference in 
 the retina which determines its shape, for here the retina seems particu- 
 larly prone to acquire an oedematous condition due to the imbibition of 
 fluid. Possibly an explanation of this condition is to be found by 
 a consideration of the vascular supply of this region. The macula is 
 abundantly supplied \vith vessels, but the central region of the fovea 
 is described as devoid of them. May not the oedematous condition 
 induced by post-mortem changes demonstrate the natural method of 
 nutrition of this region by the transudation of lymph from the sur- 
 rounding vessels ? 
 
 In No. 63 the appearance of the fundus of a foetal eye at full term 
 is exhibited. Here the ill-stretched condition of the pars optica retinae 
 is apparent. Numerous well-defined swollen folds pass radially forwards 
 from the optic disk ; the larger of these usually correspond in position 
 and direction to the larger veins, which appear not infrequently to run 
 along their most prominent surfaces. The largest and broadest fold, 
 however, disposed in the photograph almost due north, but which in 
 the normal position of the eye would be directed horizontally, differs 
 from the others in not being associated with any large vessels ; only 
 a small twig can be traced along its right edge from the region of the 
 disk. This is the plica centralis. Its remarkable resemblance to the 
 configuration of the corresponding fold in No. 62 has been already 
 referred to. At its widest part and some 4 mm. from the centre of the 
 optic disk, it exhibits a well-defined pit, in deep shadow, which marks 
 the position of the fovea centralis. The blood-vessels in this prepara- 
 tion are well displayed, the veins being distinguished from the arteries 
 by their greater size ; as they pass over the thickened lip of the collicu- 
 Ins to enter the physiological excavation of the optic disk a pronounced 
 curvature on their course is well seen. Immediately to the left of the 
 plica centralis, in the vicinity of the fovea, there seems to be an anasto- 
 mosing loop between two of the branches of one of the larger veins. 
 
 The optic disk is ill defined. The edge of the colliculus is thick 
 and rounded, through its substance the vessels are seen converging 
 to pass along the sides of the physiological cup. At the edge of the 
 
POSTERIOR HALF OF THE EYE 61 
 
 section the nervous layer of the retina appears relatively thick, as com- 
 pared with that of the adult. 
 
 For further details concerning the retina the reader is referred to 
 pp. 18 and 44. 
 
 The only evidence of the vitreous displayed in the photographs of 
 this series is seen in No. 62, where a slight cloudiness near the centre 
 is indicative of its presence, whilst around the circumference of the 
 section, within and close to the retina on the right and lower side of 
 the photograph, a filmy appearance seems to suggest the presence 
 of the hyaloid membrane. 
 
 For further details concerning the vitreous see pp. 30 and 48. 
 
 No. 66, a photograph of the separated ciliary muscle, together with 
 its nerves, has been already described in Chapter II, p. 36. No further 
 account of it is therefore necessary. 
 
KEY TO PLATES 
 
PLATE 1 
 
 Horizontal antero-posterior section through the globe of the eye of an 
 adult, viewed slightly from the front : this is the other half of the preparation 
 represented in Plate 2. 
 
 The iris is here divided to one side of the contracted pupil ; the remark- 
 able flattening of the anterior surface of the lens is well seen. About 3-8 mm. 
 to the left of the centre of the optic papilla is a dark spot (m) indicating the 
 position of the fovea centralis, which is here placed on the surface of a swollen 
 fold of retina, the plica centralis, a post-mortem appearance which affects the 
 retina in the region around the macula lutea. 
 
 a Cornea. b Sulcus sclerae, corresponding to and just behind the outer 
 sclero-corneal junction. c Attached ciliary margin of iris; this is seen to be 
 finely irregular owing to the fibres of the ligamentum pectinatum iridis ; 
 above it, will be seen the faint linear shadow thrown by the anterior edge of 
 the sulcus circularis corneae, which will be better demonstrated in other plates. 
 d Just outside the angulus iridis, which is here shown as acute owing to the 
 stretching of the iris round the contracted pupil ; d also marks the point 
 where the annular ligament is divided, to which ligament the iris, the ciliary 
 muscle, and the fibres of the pectinate ligament are attached (see Fig. I, p. 17). 
 e Ciliary process, f The iris stretched straight across the aqueous chamber ; 
 note that in this specimen the iris is cut to one side of a very contracted pupil. 
 g Thickened edges of retina at ora serrata. h Lens (lens crystallina) ; the 
 anterior flat surface is in contact with the posterior surface of the iris, i Placed 
 in the so-called canal of Petit between the fibres which form the zonule of Zinn 
 (zonula ciliaris). / Retinal vessels ; the veins are seen better than the arteries. 
 k Sclerotic (sclera). / Retina (pars optica). m The fovea centralis on the 
 surface of the plica centralis. ;/ Optic papilla (papilla n. optici) with the 
 physiological excavation (excavatio papillae n. optici) in its centre, o Chorioid 
 (chorioidea). p Lamina cribrosa. q Arteria centralis retinae, r Subarach- 
 noid space. 5 Dura-matral sheath, lined by arachnoid membrane surround- 
 ing the optic nerve, which has a pia-matral investment. 
 
PLATE 2 
 
 Horizontal antero-posterior section of the globe of the eye of an adult ; 
 opposite half of eye represented in Plate i. 
 
 The pupil is much contracted, and the anterior surface of the lens is quite 
 flat. As will be seen on comparison with the other photographs this is an 
 unusual appearance, but in no other preparation is the pupil so contracted as 
 in that seen here. The retina at the margin of the ora serrata forms a double- 
 folded edge, probably a post-mortem change. 
 
 a Cornea. b Anterior chamber (camera oculi anterior). c Sclero- 
 corneal junction. d Angulus iridis. e Ciliary body (corpus ciliare). 
 / Iris stretched right across the aqueous chamber and cut to one side of 
 a small pupil. g Lens (lens crystallina) ; anterior surface of lens remarkably 
 flattened. h Ciliary processes (processus ciliares). i Orbiculus ciliaris 
 displaying a striated appearance and covered by the pars ciliaris retinae. 
 / Ora serrata: along this edge the retina forms a thickened fold, k Retinal 
 vessels. / Sclerotic (sclera). m Retina (pars optica retinae). n Optic 
 papilla (papilla n. optici) with excavation in its centre (excavatio nervi optici). 
 o Chorioid (chorioidea). p Lamina cribrosa. q Central artery of retina 
 (arteria centralis retinae). r Subarachnoid space. 5 Dura-matral sheath of 
 optic nerve lined internally with arachnoid. 
 
PLATE 3 
 
 Vertical antero-posterior section of left eye. 
 
 Immediately behind the point of entrance of the optic nerve a worm-like 
 swelling of the retina is seen ; this is the so-called plica centralis, a post- 
 mortem change due to the action of the hardening reagent ; it corresponds in 
 position to the macula lutea. This section shows very well the sulcus circu- 
 laris corneae (d) cut across. The section also divides the ciliary body on 
 either side in the furrow between adjacent ciliary processes. It is here that 
 the fibres of the ligament of the lens are attached. Some of these fibres can 
 be faintly seen on the right-hand side of the section. 
 
 a Cornea. b Anterior chamber. c Iris. d Sulcus circularis corneae. 
 e Canal of Schlemm (sinus venosus sclerae). / Ciliary body (corpus ciliare). 
 g Ciliary process (processus ciliaris). h Ligament of lens (fibrae zonulares). 
 / Lens crystallina. j Retina, k Chorioid. / Sclerotic (sclera). m Vessels 
 of retina. n Plica centralis corresponding in position to the macula lutea. 
 o Papilla n. optici. p N. opticus. q Dura-matral sheath of optic nerve 
 (vagina n. optici). 
 
 E 2 
 
PLATE 4 
 
 Vertical antero-posterior section of eye. 
 
 To the further side of the optic papilla the plica centralis, marking the 
 position of the fovea centralis, is seen. In front of the attachment of the iris 
 the edge of the sulcus circularis corneae can be seen in shadow (c). The 
 pupillary edge and anterior surface of the iris is well displayed ; a dark spot 
 on either side marks the position of the canal of Schlemm (e). The difference 
 between the cortical and central part of the lens is clearly shown. The fibres 
 of the ligament of the lens can be seen but faintly (*). 
 
 a Cornea. b Anterior chamber (camera oculi anterior). c Sulcus 
 circularis corneae. d Iris. e Canal of Schlemm (sinus venosus sclerae). 
 / Posterior chamber (camera oculi posterior). g Ciliary body (corpus ciliare). 
 h Ciliary process (processus ciliaris). i Ligament of lens (fibrae zonulares). 
 j Retina. k Chorioid (chorioidea). / Sclerotic (sclera). m Vessels of 
 retina. n Plica centralis : corresponding to position of macula lutea and fovea 
 centralis. o Optic papilla (papilla n. optici). p Dura-matral sheath of optic 
 nerve (vagina n. optici). q Optic nerve. r Arteria centralis retinae. 
 
PLATE 5 
 
 Antero-posterior section of the eye of a man aged thirty-nine. 
 The section passes through the optic papilla posteriorly and divides the 
 iris in front to the near side of the pupil. The preparation shows very well 
 the ora serrata and the pars ciliaris retinae (orbiculus ciliaris). The retina 
 has in places separated from the chorioid, and the chorioid is observed apart 
 from the sclerotic. In this view the ligament of the lens is not seen. 
 
 a Cornea. b Anterior chamber (camera oculi anterior), c Iris, cut 
 across to the near side of the pupil. d Posterior chamber (camera oculi 
 posterior). e Ciliary body (corpus ciliare). / Ciliary processes (processus 
 ciliares). g Lens crystallina. h Pars ciliaris retinae, orbiculus ciliaris 
 displaying a striated appearance. i Ora serrata the edge of the pars 
 optica retinae. / The retina detached from the chorioid. k Chorioid 
 (chorioidea), detached from the sclera, here displays the fibres of the lamina 
 fusca. / Sclerotic (sclera). m Optic papilla (papilla n. optici) with the 
 optic cup (excavatio papillae n. optici) in its centre. n Dura-matral sheath 
 of optic nerve (vagina n. optici). o Optic nerve. p Arteria centralis 
 retinae. 
 
PLATE' 6 
 
 Antero-posterior section through the eye of a man aged thirty-nine. Same 
 specimen as Plate 5. 
 
 The lens with its capsule and the vitreous have been removed ; immediately 
 in front of the attached margin of the iris the shadow cast by the sulcus 
 circularis corneae can be seen. The ciliary processes are well displayed and 
 the orbiculus ciliaris is well shown. The retina is in great part detached, 
 but along the line of the ora serrata it is seen to be more firmly fixed to the 
 subjacent structures ; posteriorly the optic cup is clearly shown. 
 
 a Cornea. b Anterior chamber (camera oculi anterior), c Iris: immedi- 
 ately in front of its attached circumference evidence of the sulcus circularis 
 corneae may be seen. d Ciliary body (corpus ciliare). e Ciliary process 
 (processus ciliaris). f Orbiculus ciliaris with meridional fibres. g Ora 
 serrata. h Retina (pars optica retinae), i Chorioid (chorioidea). j Sclerotic 
 (sclera). k Retinal vessels. / Optic papilla and optic cup (excavatio n. 
 optici). m Optic nerve. n Dura-matral sheath of optic nerve (vagina n. 
 optici). o Arteria centralis retinae. 
 
PLATE 7 
 
 Anterior half of an antero-posterior section of the eye viewed obliquely 
 from behind. 
 
 The ora serrata is well seen ; along this goffered edge the retina is seen 
 to be more firmly attached to the subjacent chorioid than it is posteriorly. 
 The radial arrangement of the orbiculus ciliaris is clearly shown on the left of 
 the specimen. The pigmented posterior surface of the iris (pars uvealis 
 iridis) is displayed, forming the anterior wall of the posterior chamber (camera 
 oculi posterior). In this photograph the light has failed to catch the fibres of 
 the ligament of the lens, so that they are not revealed in the specimen. 
 
 a Cornea. b Anterior chamber (camera oculi anterior). c Pupillary 
 margin of iris. d Posterior chamber (camera oculi posterior) with the 
 posterior pigmented surface of the iris in front, and the blunt anterior 
 extremities of the ciliary processes projecting into it posteriorly ; the zonule 
 of Zinn is not here seen. e Ciliary body (corpus ciliare). / Ciliary 
 processes (processus ciliares). g Lens (lens crystallina). h Orbiculus 
 ciliaris overlain by the pars ciliaris retinae. /' Ora serrata. / Retina. 
 k Chorioid (chorioidea). / Sclerotic (sclera). 
 
PLATE 8 
 
 Antero-posterior section through the fore part of the globe of the eye. 
 
 This section shows very well the suspensory ligament of the lens, particularly 
 on the left side. As will be seen, the fibres of the zonule of Zinn (zonula 
 ciliaris) spring from the ciliary body and the orbiculus ciliaris (see PL 37); 
 they separate as they pass to the lens, some going to the front, others to the 
 posterior surface of that structure; between the diverging fibres and the 
 circumference of the lens is a space shown in section g, the canal of Petit 
 or the spatia zonularia. The section also displays the relationship of the 
 sulcus sclerae (c), at the junction externally of the cornea and sclerotic, to the 
 sulcus circularis corneae (e) situated at the angulus iridis. 
 
 a Cornea. b Anterior chamber (camera oculi anterior). c Sulcus sclerae. 
 d Iris, e Sulcus circularis corneae. / Posterior chamber bounded behind 
 by the ciliary processes and the ligament of the lens. g The canal of Petit 
 (spatia zonularia) with the zonular fibres (fibrae zonulares) in front and behind. 
 h Ciliary body (corpus ciliare). i Ciliary process (processus ciliaris). / Lens 
 crystallina. k Orbiculus ciliaris. / Ora serrata. m Retina. Chorioid. 
 o Sclera. p Corpus vitreum. 
 
PLATE 9 
 
 Antero-posterior section through an eye in which, owing to the result of an 
 injury, the anterior surface of the iris has become closely adherent to the 
 internal surface of the cornea. 
 
 The posterior chamber has thus become enormously enlarged at the 
 expense of the anterior chamber, which has in consequence been completely 
 obliterated. As a result a sort of natural dissection has ensued, and the 
 specimen has been included because it affords an admirable demonstration of 
 the two layers of the zonule of Zinn with the so-called canal of Petit between. 
 As is well seen here, and also in some of the other sections (Pis. i, 2, 8), the 
 circumference of the lens is blunt and furnished with two edges, to the anterior 
 of which the fibres of the suspensory ligament can be seen passing to be 
 attached to the capsule of the lens, whilst the posterior sheet, in contact 
 with the hyaloid membrane, is seen to blend with the capsule of the lens at its 
 posterior edge. 
 
 a Injured cornea. b Greatly distended posterior chamber (camera oculi 
 posterior) ; the uveal surface of the iris is exposed, as the iris is spread over 
 the inner surface of the cornea, c The anterior ends of the ciliary processes 
 pulled forwards by the structural folds of the iris. d Ciliary body (corpus 
 ciliare). e Anterior fibres of zonule of Zinn, forming the suspensory ligament 
 of the lens, f Posterior layer of zonule of Zinn ; between the two is the 
 so-called canal of Petit. g Lens (lens crystallina) : note its blunt circum- 
 ference, h Orbiculus ciliaris. i Ora serrata. j Sclerotic (sclera). k Retina 
 (pars optica retinae). / Optic papilla with excavation. 
 
PLATE 1O 
 
 n 
 
 Antero-posterior section through the eye. 
 
 The pupil is widely dilated, with consequent thickening of the iris, which 
 at its circumference is now seen to occupy almost completely the sulcus 
 circularis corneae (d). The vitreous is in situ ; its delicate hyaloid membrane 
 (membrana hyaloidea) is well displayed to the right of the entrance of the 
 optic nerve ; its fine connexions with the surface of the retina are also seen. 
 
 a Cornea. b Anterior chamber (camera oculi anterior). c Iris, with 
 widely dilated pupil. d Sulcus circularis corneae, fully occupied by the 
 contracted and thickened iris. e Ciliary body (corpus ciliare). / Processus 
 ciliaris. g Faint indications of the ligament of the lens. h Ora serrata. 
 i Retina. / Chorioid (chorioidea). k Sclerotic (sclera). / Hyaloid mem- 
 brane (membrana hyaloidea) : its connexions with the retina are also visible. 
 m Optic nerve. 
 
PLATE 11 
 
 Antero-posterior section through the eye (same eye as Plate 10). 
 The vitreous has been removed with the hyaloid membrane, a tag of which 
 is seen still attached to the circumference of the lens on the left side. The 
 retina has been taken away, and the iris has also been removed. The sulcus 
 circularis cornea is well shown ; immediately below the sulcus on the left side 
 may be seen the surface from which the iris has been torn away, correspond- 
 ing to the annular ligament (ligamentum annulare). The relation of the sulcus 
 circularis corneae (d) to the sulcus sclerae (c) is also displayed. The pig- 
 mented pars ciliaris retinae has been stripped off from a considerable surface of 
 the orbiculus ciliaris immediately in front of the ora serrata. 
 
 a Cornea. b Anterior chamber (camera oculi anterior) : through the 
 removal of the iris the anterior and posterior chambers have been thrown 
 into one. c Sulcus sclerae at outer surface of sclero-corneal junction. 
 d Sulcus circularis corneae : on the left-hand side of the section this is seen 
 quite distinct from the surface from which the iris has been torn away. 
 e Ciliary body (corpus ciliare). / Ciliary processes (processus ciliares). 
 g Lens (lens crystallina) in situ, h Surface of orbiculus ciliaris from which 
 the pigmented pars ciliaris retinae has been stripped off. i Chorioid 
 (chorioidea). / Sclerotic (sclera). k Optic papilla (papilla n. optici). 
 
PLATE 12 
 
 Antero-posterior section through the eye (same preparation as Plates 10 and u). 
 The lens with its capsule and the vitreous have been removed. The 
 iris has been torn away from its attachment, and the retina has been taken 
 away, leaving much of its pigment layer attached to the chorioid. Along the 
 line of the ora serrata the pigmented portion of the pars ciliaris retinae has 
 been completely stripped away, though anteriorly it remains as it passes 
 forwards over the ciliary processes. The relation of the sulcus sclerae (c) to 
 the sulcus circularis corneae (d) is well displayed, and the latter is well seen 
 immediately in front of the surface from which the iris has been torn away 
 near the corneo-scleral margin. 
 
 a Cornea. b Anterior chamber (camera oculi anterior). c Sulcus sclerae 
 at corneo-scleral margin. d Sulcus circularis corneae : on the left-hand side 
 of the section this is seen quite distinct from the surface from which the iris 
 has been detached. e Ciliary body (corpus ciliare). / Ciliary processes 
 (processus ciliares). g Surface of orbiculus ciliaris from which the pigmented 
 pars ciliaris retinae has been stripped. h Chorioid (chorioidea). i Sclerotic 
 (sclera). / Optic papilla (papilla n. optici). 
 
PLATE 13 
 
 Antero-posterior section through the eye (same eye as Plates IQ, n, and 12). 
 
 All the contents of the globe have been removed, leaving only the cornea 
 and sclerotic. The proportionate thickness of the cornea to the sclerotic is 
 well seen. The perichorioideal space, between the choroid and the sclerotic, 
 has been exposed by the removal of the choroid ; and the lamina fusca, which 
 connects the latter to the former, has been torn through, leaving a certain 
 amount of pigmented tissue adherent to the inner surface of the sclerotic. 
 The perichorioidal space is traversed by the posterior ciliary arteries and 
 the ciliary nerves, the courses of which are indicated by lighter tracts running 
 through the pigmented tissue. 
 
 a Cornea. b Sulcus circularis corneae. c Indicates the line of attach- 
 ment of the ora serrata. d Light tracts, indicating the course and position of 
 some of the ciliary nerves. e One of the posterior ciliary arteries, f Marks 
 point of exit through the sclerotic of one of the venae vorticosae. g Sclerotic 
 (sclera). h Optic papilla (papilla n. optici). 
 
PLATE 14 
 
 This view represents a quarter of the ocular globe cut irom pole to pole. 
 
 ,This method of section has been adopted so as to enable the iris to be 
 pulled back without any damage. The lens with its ligament and the vitreous 
 have been removed. The quadrant of the iris has been drawn back in order to 
 open up the angle of the iris and thus expose the sulcus circularis corneae (c). 
 The vertical striae revealed at the bottom of the sulcus are due to the arrange- 
 ment of the fibres of the ligamentum pectinatum iridis, the intervals between 
 which communicate with the spaces of Fontana. 
 
 a Cornea. b Anterior chamber (camera oculi anterior). c Sulcus 
 circularis corneae, at the bottom of which the vertically disposed fibres of the 
 pectinate ligament (ligamentum pectinatum iridis) can be faintly seen. d The 
 iris pulled back. e Ciliary body (corpus ciliare). / Ciliary process. 
 g Orbiculus ciliaris. h Ora serrata : here the oedema of the pars optica 
 retinae, due either to post-mortem changes or the influence of the preservative, 
 is very definitely limited in front in harmony with the attached edge of the 
 ora serrata. i Retina. / Chorioid (chorioidea). k Sclerotic (sclera). 
 
PLATE 15 
 
 Antero-posterior view through the eye of a full-time foetus (lived one day). 
 
 Note the absolute and proportionately greater thickness of the cornea, the 
 shallow anterior chamber, the more spherical lens, and the smaller ciliary 
 body. The retina is thicker and thrown into folds. How much of this is due 
 to post-mortem change or the use of preservatives it is difficult to say, but 
 possibly the occurrence of these folds in the living accounts for the ' shot J or 
 'watered silk' appearance of the retina revealed on the ophthalmoscopic 
 examination of the eyes of young children. There is a tag of tissue (m) 
 extending forwards from the optic papilla ; this is probably a fold of retina 
 which has been divided on the near half of the section. The ora serrata is 
 seen to lie much nearer the ciliary body than in the adult. 
 
 a Cornea. b Anterior chamber (camera oculi anterior). c Pupillary 
 margin of iris. d Canal of Schlemm (sinus venosus sclerae). e Ciliary body 
 (corpus ciliare). / Ciliary processes (processus ciliares). g Ora serrata, 
 placed nearer the ciliary body than in the adult, and forming what appears 
 to be a thick reduplicated margin. h Lens (lens crystallina), much more 
 spherical than in the adult. /' Retina, j Choroid (chorioidea). k Sclera. 
 / The shrunken vitreous with hyaloid membrane (membrana hyaloidea). 
 m Tag of tissue, due probably to a cut fold of retina. n Papilla n. optici. 
 o Optic nerve. p Arteria centralis retinae. q Spatium intervaginale. 
 r Dura-matral sheath of optic nerve. 
 
PLATE 16 
 
 Antero-posterior section through the eye of a foetus about 6 months. 
 
 Note the very thick cornea, the spherical lens, and the redundant and folded 
 retina, particularly anteriorly on the region which ultimately develops into 
 the ora serrata. 
 
 The pupillary membrane, extending across the anterior chamber, is seen 
 in section immediately behind the posterior surface of the cornea. 
 
 a Sclerotic (sclera). b Perichorioidal space. c Redundant fold of 
 retina corresponding to position of ora serrata. d Chorioid (chorioidea). 
 e Ciliary border of iris. f Pupillary membrane (membrana pupillaris). 
 g Lens (lens crystallina), spherical in shape. h Cornea: note its great 
 proportionate thickness. i Vitreous and hyaloid membrane. j Ciliary 
 process (processus ciliaris). k Thick retinal layer. / Chorioid. 
 
PLATE 17 
 
 Antero-posterior section through the eye of a foetus of 6 months. 
 This is the same specimen as PL 16, only differently lighted and viewed so 
 as to exhibit the hyaloid artery running forwards from the back of the vitreous 
 chamber to the posterior surface of the lens. 
 
 a Cornea. b Iris. c Ciliary process (processus ciliaris). d Lens 
 (lens crystallina). e Redundant anterior margin of retina (pars optica). 
 / Sclerotic (sclera). g Perichorioidal space. h Hyaloid artery (arteria 
 hyaloidea). * Retina. / Chorioid (chorioidea). k sclerotic (sclera). 
 
 1IS4 
 
PLATE 18 
 
 Antero-posterior section through the globe of the eye of a 6J-months y 
 foetus (same foetus as Pis. 16 and 17). 
 
 The lens with the vitreous, together with part of the retina (pars optica) 
 near the ora serrata, and part of the pars ciliaris (see PL 57), have been 
 removed. Note the great proportionate'thickness of the cornea, the pupillary 
 membrane (b), and the thick and redundant retina (pars optica). The stalk of 
 the hyaloid artery (k) torn across before it enters the vitreous. 
 
 a Cornea. b Pupillary membrane : its connexion with the iris (c) is seen. 
 c Iris. d Retina near the ora serrata; the edge is torn here, as some of 
 the retina has been removed : see the specimen photographed in PL 57. 
 e Ciliary processes (processus ciliares). / Orbiculus ciliaris, from which the 
 pars ciliaris retinae has been torn away. g Ciliary body (corpus ciliare). 
 h Sclerotic (sclera). * Chorioid (chorioidea): the suprachorioidal layer is 
 well seen. / Thick retina (pars optica). k Remains of hyaloid artery torn 
 away anteriorly. 
 
PLATE 19 
 
 View of the anterior surface of the eyeball, the cornea having been cut 
 away and the anterior chamber laid open. 
 
 Under the thin edge, where the cornea has been cut away on the right 
 side of the preparation, some of the fibres of the pectinate ligament can be 
 seen, (g) with the openings of the spaces of Fontana in between them. 
 
 a Outer surface of sclerotic (sclera). b Cut edge of ocular conjunctiva. 
 c Sclero-corneal margin cut through and cornea removed. d Anterior 
 chamber (camera oculi anterior), with anterior surface of iris behind. 
 c Pupillary margin of iris (margo pupillaris iridis). / Lens (lens crystallina) 
 seen through pupil. g Fibres of the pectinate ligament (ligamentum 
 pectinatum iridis), with openings of the spaces of Fontana (spatia anguli 
 iridis). h Circular folds of iris. i Radial folds of iris (plicae iridis). 
 
 F 2 
 
PLATE 2O 
 
 Anterior view of the eye, the cornea and sclerotic having been removed. 
 
 The angulus iridis is thus exposed from the front (c), and the fibres passing 
 from the cornea to the front of the iris, which constitute the ligamentum 
 pectinatum iridis, are well displayed ; in the intervals between these fibres 
 there are openings leading into the crypt-like spaces the spaces of Fontana. 
 Just external to the margo ciliaris of the iris (c) may be seen a narrow annular 
 band surrounding the iris : this marks the anterior attachment of the meri- 
 dional fibres of the ciliary muscle to the internal scleral process (ligamentum 
 annulare). 
 
 a Chorioid (chorioidea). b Scleral surface of the ciliary body (corpus 
 ciliare). c Marks the position of the spaces of Fontana (spatia anguli iridis), 
 the openings of which appear between the fibres of the pectinate ligament 
 (ligamentum pectinatum iridis). Just external to c may be seen the line of 
 attachment of the anterior ends of the meridional fibres of the ciliary muscle. 
 d Convexity of the iris overlying the sphincter pupillae. e The pupillary 
 margin of the iris (margo pupillaris iridis). f Lens seen through pupil. 
 g Circular folds of the iris. h Radial folds of the iris (plicae iridis). * Venae 
 vorticosae of the choroid. j Long posterior ciliary artery (arteria ciliaris 
 posterior longa). k Ciliary nerve (n. ciliaris). 
 
PLATE 21 
 
 Anterior view of the front of a deeply pigmented iris, with the annulus 
 ciliaris (ciliary muscle) of the ciliary body attached. 
 
 On the front of the iris concentric and radial folds are seen ; just outside 
 the ciliary attachment of the iris (c) there is a ring of white tissue ; this is the 
 annular ligament (ligamentum annulare), which has been torn away from the 
 sclerotic close to the sclero-corneal junction (see Plate 47) ; hereto are attached 
 the fibres which pass to the iris (ligamentum pectinatum) and the fibres which 
 afford attachment to the anterior insertion of the meridional fibres of the ciliary 
 muscle. The iris is too deeply pigmented to show well the fibres of the 
 pectinate ligament and the openings of the spaces of Fontana, but slight 
 indications of the former can be seen at the point marked g. 
 
 a Scleral surface of ciliary body (corpus ciliare). b Annular ligament torn 
 through (ligamentum annulare). (c) Ciliary border of iris (margo ciliaris iridis). 
 d Concentric folds on front of iris. e Pupillary margin, thick and rounded 
 in front, thin and sharply defined behind (margo pupillaris iridis). / Pupillary 
 aperture (pupilla). g Indicates the position where some of the fibres of the 
 ligamentum pectinatum can be faintly seen. h Ciliary nerves forming plexus. 
 
PLATE 22 
 
 Anterior view of detached deeply pigmented iris. 
 
 The pupil (d) is fairly widely dilated, its posterior margin is thin and sharp, 
 but its external circumference is thick and bevelled, as seen in shadow on 
 the right side of the specimen. The concentric furrowing (e) of the anterior 
 surface is well marked, as are also the radial plicae (b). 
 
 a External margin of iris torn away from the ciliary body (margo ciliaris 
 iridis). b Radial plica. c Pupillary margin of iris (margo pupillaris iridis). 
 d Pupillary aperture (pupilla). e Concentric plicae. 
 
PLATE 23 
 
 View of the posterior surface of the detached iris. 
 
 This lorms the anterior wall of the posterior chamber. Owing to the 
 presence of the deeply pigmented uveal layer (pars iridica retinae or stratum 
 pigmenti iridis) this surface is difficult to photograph and the details of its 
 structure are necessarily obscure. Numerous radial folds (the structural 
 folds of Schwalbe) are seen passing from the ciliary attachment inwards 
 towards the pupil (b). Some of these folds are seen torn across at the upper 
 part of the ciliary margin, and to their presence is due the irregular outline of 
 the inner edge of the torn ciliary border. About i mm. from the pupillary 
 edge these large folds are replaced by numerous smaller ones (e). These 
 are the so-called contraction folds of Schwalbe, and form the pupillary zone 
 (Fuchs). 
 
 a Ciliary margin of iris, torn through (margo ciliaris iridis). The inner 
 edge of this margin is irregular in outline, due to the structural folds being 
 torn across. b Posterior surface of iris covered with the uveal layer formed 
 by the pars iridica retinae ; here the structural folds passing from the ciliary 
 border inwards to the pupil may be seen. c Pupillary margin (margo pupil- 
 laris iridis) : as seen from behind, this is a thin edge with a finely crenated 
 border. d Pupillary aperture (pupilla). e Faintly seen are the fine folds 
 (contraction folds of Schwalbe) forming the pupillary zone of Fuchs. 
 
PLATE 24 
 
 View of the anterior surface of the eye, the sclerotic and cornea having 
 been removed. 
 
 The right half of the iris has been cut away so as to open the posterior 
 chamber, the posterior wall of which is thus exposed ; this is seen to be 
 formed from without inwards by the blunt anterior extremities of the ciliary 
 processes (e), the zonule of Zinn (zonula ciliaris) (d), composed of the fibres 
 which form the ligament of the lens ; and the anterior surface of the lens (/). 
 The cut edge of the ciliary margin of the iris (c) is shown, and certain narrow 
 folds (j) are seen divided. These are the radially arranged folds which pass 
 from the fore part of the ciliary body and ciliary processes on to the posterior 
 surface of the iris, converging towards the pupillary margin (see Pis. 42, 52). 
 On the left and upper side of the preparation the outer layer of the ciliary body 
 has been dissected away so as to expose the meridional fibres of the ciliary 
 muscle and the vascular and nervous plexuses within its substance. Close to 
 the ciliary margin of the iris on the left side can be seen some of the fibres of 
 the pectinate ligament and the openings of the spaces of Fontana. 
 
 a Chorioid (chorioidea). b Meridional fibres of ciliary muscle, together 
 with vessels and nerves. c Cut peripheral attachment of iris (margo ciliaris). 
 d Zonule of Zinn, suspensory ligament of the lens. e Anterior extremities 
 of the ciliary processes seen in shadow. / Lens (lens crystallina). g Pupil- 
 lary margin of iris (margo pupillaris). h Fibres of the pectinate ligament with 
 the openings of the spaces of Fontana (spatia anguli iridis). i Cut edge 
 of iris. j Folds cut passing from ciliary body and processes to posterior 
 surface of iris (structural folds of Schwalbe). k Outer surface of ciliary body 
 (corpus ciliare). / Ciliary nerves breaking up to form plexus. m Divided 
 edge where superficial part of ciliary body has been removed. 
 
PLATE 25 
 
 This is the same specimen as PL 24, except that the iris has now been 
 completely removed, thus laying open the whole of the posterior chamber. 
 
 The lens in the centre is suspended by its ligament (zonule of Zinn), the 
 fibres of which are faintly visible in the shadow surrounding the lens, passing 
 from the circumference of the lens towards the inner surface of the ciliary 
 body ; the rounded ends of the ciliary processes are dimly seen on a plane 
 anterior to the zonule of Zinn. In front of these are seen a number of thin 
 white projecting folds. These are the structural folds of Schwalbe, which 
 have been divided as they pass from the fore part of the ciliary body and 
 processes to the posterior surface of the iris. The other details are the same 
 as in PL 19. 
 
 a Chorioid (chorioidea). b Meridional fibres of ciliary muscle, together 
 with vessels and nerves. c Cut peripheral attachment of iris (margo ciliaris 
 iridis). d Zonule of Zinn ; suspensory ligament of lens seen in shadow. 
 e Anterior rounded extremities of the ciliary processes (processus ciliares), seen 
 in shadow, f Lens (lens crystallina). g Divided folds (structural folds of 
 Schwalbe), passing from fore part of ciliary body and ciliary process to the 
 posterior surface of the iris. h Ciliary nerves breaking up to form plexus. 
 / Outer (scleral) surface of ciliary body ; near this the cut edge is seen where 
 the superficial layer has been removed to expose the ciliary muscle. 
 
PLATE 26 
 
 View of the anterior surface of the eye of a full-time foetus. 
 
 The cornea and sclerotic having been removed, the anterior chamber is 
 laid open and the angulus iridis (e) is thus exposed. Here some of the fibres 
 of the ligamentum pectinatum iridis are exposed, with the openings between 
 them of the spaces of Fontana (spatia anguli iridis); these, however, are 
 better seen in PL 20. Immediately external to the attached margin of the 
 iris (margo ciliaris) is an annular band of tissue, sometimes called the annular 
 ligament (ligamentum annulare, annulus tendinosus), from which the meri- 
 dional fibres of the ciliary muscle arise. 
 
 This preparation likewise shows the radial arteries of the iris (e), passing 
 from the circulus major externally to the circulus minor near the pupillary 
 edge. 
 
 a Chorioid (chorioidea). b External or scleral surface of the ciliary 
 body (corpus ciliare). c Annular ligament (ligamentum annulare). d Fibres 
 of pectinate ligament (ligamentum pectinatum), between which are the 
 openings of the spaces of Fontana (spatia anguli iridis). e Radial folds 
 in which may be seen vessels passing from the circulus major externally 
 to the circulus minor near the pupillary edge. / Anterior surface of iris, 
 forming posterior wall of anterior chamber. g Lens (lens crystallina), seen 
 through the pupil. h Pupillary margin of iris (margo pupillaris). i Long 
 posterior ciliary artery. / Ciliary nerve. 
 
PLATE 27 
 
 View of the anterior surface of the eye, the cornea and a ring of sclerotic 
 having been removed. 
 
 The iris has also been completely torn away. The posterior chamber is 
 fully exposed. The lens, surrounded by the zonule of Zinn, is well shown, 
 and the relation of the ciliary processes thereto is clearly seen. The specimen 
 has been photographed by a combination of reflected and transmitted light ; 
 the latter shines through the anterior half of the globe of the eye, which has 
 been divided equatorially. In this way the details of the ligament of the lens 
 (zonule of Zinn) are better displayed. 
 
 a External surface and sclerotic (sclera). b Cut edge of sclerotic, which 
 has been divided wide of the sclero-corneal junction. c Fore part of the 
 external surface of the ciliary body (corpus ciliare), exposed. d Lens (lens 
 crystallina). e Figured in solid black, the anterior extremities of the ciliary 
 processes (processus ciliares), which project into the posterior chamber. 
 / Fibres of the suspensory ligament (zonula ciliaris), passing from the inner 
 surface of the ciliary body to the circumference of the lens. As will be seen 
 from an inspection of the photograph stereoscopically, these do not all lie 
 in the same plane. 
 
PLATE 28 
 
 View of the anterior aspect of the eye. Same specimen as PI. 29. 
 The cornea has been removed' at the sclero-corneal junction, and the iris 
 has been completely taken away, thus opening up the posterior chamber, and 
 exposing its posterior wall, formed from without inwards by the anterior 
 extremities of the ciliary processes (/), the zonule of Zinn, and the anterior 
 surface of the lens. The fibres of the zonule are well seen, and on the left 
 side of the specimen a faint shadow cast by the lens is seen on the anterior 
 surface of the vitreous. 
 
 a External surface of sclerotic (sclera). b Ocular conjunctiva, c Sclerotic, 
 cut close to sclero-corneal junction, d Zonule of Zinn, with the fibres of the 
 suspensory ligament of the lens faintly seen. e Lens with spots of pigment 
 indicating the position of the pupillary margin of the iris. / Anterior 
 extremities of the ciliary processes (processus ciliares). 
 
PLATE 29 
 
 The same specimen as Plate 28, viewed by transmitted and reflected light. 
 
 The cornea and iris have been removed, and the posterior chamber has been 
 laid open, displaying its posterior wall ; from without inwards this is formed by 
 the rounded anterior ends of the ciliary processes (/), the zonule of Zinn (d), 
 and the anterior surface of the lens. 
 
 a External surface of the sclerotic (sclera). b Ocular conjunctiva. 
 c Sclerotic, cut at sclero-corneal margin. d Zonule of Zinn (zonula ciliaris), 
 with the fibres of the suspensory ligament of the lens faintly seen. e Ante- 
 rior surface of the lens (lens crystallina), with spots of pigment on it derived 
 from the posterior layer of the iris, indicating the position of the pupillary 
 margin. / Anterior extremities of the ciliary processes (processus ciliares). 
 
PLATE 3O 
 
 The same specimen as Plates 28 and 29, viewed by transmitted light only. 
 
 The cornea and iris have been removed. The clear ring corresponds to the 
 zonule of Zinn (d) and exhibits the faint striation due to the fibres of the 
 suspensory ligament of the lens. Externally the zonule is limited by the 
 irregular outline of the ciliary processes (b), whilst internally its edge corre- 
 sponds to the circumference of the lens (c). 
 
 a Sclerotic, covered anteriorly by the ocular conjunctiva, b Irregular out- 
 line due to the projection of the anterior extremities of the ciliary processes 
 (processus ciliares). c The lens (lens crystallina) ; the edge appears crenated 
 where the fibres of the suspensory ligament are attached to it. d Zonule of 
 Zinn (zonula ciliaris) ; the faintly striated appearance is due to the fibres of the 
 suspensory ligament of the lens. 
 
PLATE 31 
 
 View of the anterior aspect of the globe of the eye ; the cornea, part of the 
 sclerotic, and the whole of the iris having been removed. 
 
 The posterior chamber is fully exposed ; the structures which lie in relation 
 to its posterior wall are fully seen, viz. : the anterior ends of the ciliary pro- 
 cesses externally (/), the zonule of Zinn with the fibres of the suspensory liga- 
 ment of the lens (h), and the anterior surface of the lens internally (^). The 
 anterior part of the scleral surface of the ciliary body is also seen, and the edge 
 where the iris has been torn away (e) is shown. 
 
 a Outer surface of sclerotic (sclera). b Ocular conjunctiva overlying the 
 sclerotic. c Cut edge of sclerotic wide of sclero-corneal junction. d Scleral 
 surface of anterior part of ciliary body (corpus ciliare). e Edge where iris has 
 been torn away from ciliary body. / Anterior rounded extremities of the 
 ciliary processes (processus ciliares). g Anterior surface of the lens, with 
 some pigment adherent to it derived from the pupillary margin of the iris. 
 h Zonule of Zinn (zonula ciliaris) ; the fibres of the suspensory ligament of the 
 lens are clearly shown, and their attachment to the circumference of the lens, 
 where they form a crenated edge, is well seen. i One or two of the folds 
 (structural folds of Schwalbe), passing from the ciliary body to the posterior 
 surface of the iris, are shown torn across. 
 
PLATE 32 
 
 View of the anterior surface of the globe of the eye of an eighth-month 
 foetus. 
 
 The cornea and iris have been removed and the posterior chamber exposed. 
 The specimen has been photographed by a combination of both reflected 
 and transmitted light, so that the zonule of Zinn appears as a light ring 
 between the lens and the ciliary processes. The fibres of the ligament of the 
 lens are visible as a series of fine striae radially disposed ; it is worthy of 
 note that their attachment to the circumference of the lens is not marked by 
 any crenation of the margin as seen in the older specimens, due probably 
 to the fact that these attachments have not been strained by the use of the 
 mechanism of accommodation. 
 
 a External surface of sclerotic (sclera). b Thick divided edge of sclerotic 
 near sclero-corneal junction, c Lens (lens crystallina), faintly marked with four 
 radial striae. d Zonule of Zinn (zonula ciliaris), with radial striae indicating 
 the fibres of the suspensory ligament of the lens. e Ciliary processes (pro- 
 cessus ciliares). 
 
PLATE 33 
 
 View of the interior of the anterior half of the globe of the eye. 
 In this specimen the vitreous body is in situ and little disturbed, its hyaloid 
 membrane being undetached and closely adherent to the inner surface of the 
 retina. In the centre the lens is seen surrounded by a dark ring, the zonule 
 of Zinn, external to which the corona ciliaris is displayed ; the orbiculus ciliaris, 
 lying between the corona and the ora serrata, is shown, and the striation of 
 its structure is clearly visible. On the left side the serrated edge of the ora 
 serrata is seen, and the tendency of the retina to form a thickened fold 
 immediately behind it, due probably to post-mortem changes or the action of 
 the preservative, is very distinctly demonstrated. 
 
 a Sclerotic (sclera). b Retina. c Orbiculus ciliaris. d Chorioid 
 (chorioidea). e Lens (lens crystallina). / Corona ciliaris, formed in this 
 preparation of sixty-seven ciliary processes (processus ciliares). g Zonule 
 of Zinn (zonula ciliaris) ; owing to the shadow but faint traces of the fibres of 
 the ligament of the lens are to be seen. h Ora serrata. i Thickened fold 
 of retina close to posterior edges of ora serrata. 
 
 1254 
 
PLATE 34 
 
 View of the interior of the anterior half of the globe of the eye, taken by 
 reflected light. 
 
 In the centre is the lens, surrounded by the zonule of Zinn ; in deep shadow 
 only very slight suggestions of the striated arrangement of the suspensory 
 ligament of the lens can be seen. Surrounding the dark zonule is the corona 
 ciliaris, made up of seventy-eight ciliary processes in this specimen. In this 
 preparation the ciliary processes are not all equal in size; large and small 
 seem to alternate, particularly in the upper part of the corona. Between the 
 corona and the ora serrata the orbiculus ciliaris with its radial striae is visible. 
 The position of the ora serrata is apparent, and its notched border is well 
 displayed in the upper part of the specimen. 
 
 a Sclerotic (sclera). b Retina (pars optica). c Ora serrata. d Orbi- 
 culus ciliaris. e Corona ciliaris, made up of seventy-eight ciliary processes. 
 / Posterior surface of the lens (lens crystallina). g Ciliary process (processus 
 ciliaris). h Zonule of Zinn (zonula ciliaris). i Chorioid (chorioidea). 
 
PLATE 35 
 
 View of the interior of the anterior half of the globe of the eye, viewed by 
 reflected light : the same specimen as Plate 31. 
 
 In the centre is seen the lens ; around its circumference there is a narrow 
 dark annular zone, the zonule of Zinn ; here and there the striation produced 
 by the fibres of the suspensory ligament can be faintly seen (e). External to 
 the zonule, the corona ciliaris, formed by seventy or more ciliary processes, is 
 well displayed (d and /). Wide of the elevations produced by the ciliary 
 processes the orbiculus ciliaris is shown. The ora serrata of the retina is 
 somewhat obscured by the puckering of the hyaloid membrane of the vitreous 
 body. 
 
 a Sclerotic (sclera). b Chorioid (chorioidea). c Retina (pars optica retinae). 
 d Orbiculus ciliaris. e Zonule of Zinn (zonula ciliaris) : the fibres of the 
 suspensory ligament of the lens can be faintly seen, f Posterior surface of 
 the lens (lens crystallina) ; along its circumference may be seen the points of 
 attachment of some of the suspensory fibres. g The corona ciliaris, formed 
 by the eighty-one ciliary processes here present. h The vitreous and puckered 
 hyaloid membrane. i Ciliary process (processus ciliaris). 
 
 G 2 
 
PLATE 36 
 
 View of the interior of the anterior half of the globe of an adult eye. 
 
 This photograph has been introduced because it shows very well the 
 arrangement of the lamellae of the lens, as seen from behind, to form the posterior 
 lens star. As will be seen in this specimen, the tissue of the lens is disposed 
 in eight wedge-shaped masses. 
 
 The lens also displays around its circumference the two-edged appearance 
 exhibited in Plate 39. The vitreous and hyaloid membrane have been 
 removed from the posterior surface of the lens, but the connexion of the two 
 seems to correspond to the posterior edge of the circumference of the lens. 
 To the anterior margin of the circumference may be seen passing the fibres of 
 the suspensory ligament of the lens. 
 
 a Sclerotic (sclera). b Torn edge of the hyaloid membrane. c Corona 
 ciliaris, formed of eighty-one ciliary processes (processus ciliares). d Zonule 
 of Zinn (zonula ciliaris) ; the fibres of the suspensory ligament of the lens 
 are here seen passing to the anterior aspect of the circumference of the lens. 
 e Posterior surface of the lens (lens crystallina), showing the lens star. 
 /Retina (pars optica). g Ridged and striated orbiculus ciliaris. 
 
PLATE 37 
 
 View of the interior of the anterior half of the globe of the eye of an adult. 
 
 The vitreous has been removed, but the torn edge of the hyaloid membrane 
 is seen at c. 
 
 This preparation is included because it displays very well the disposition 
 of the fibres of the zonule of Zinn which are derived from the pars ciliaris 
 retinae of the orbiculus ciliaris. These fibres are particularly well seen on the 
 right side of the specimen, in which, owing to the removal of the vitreous, they 
 appear as withdrawn from the furrows which lie between the ciliary processes. 
 The circumference of the lens displays a double edge: one in front, to which the 
 fibres of the anterior part of the zonule are attached ; and one behind, where the 
 lens lies in contact with the fossa patellaris formed by the anterior surface of 
 the hyaloid membrane of the vitreous body. 
 
 a Chorioid (chorioidea). b Retina (pars optica). c Torn edge of hyaloid 
 membrane, d Corona ciliaris, formed of eighty- two ciliary processes (processus 
 ciliares). e Zonule of Zinn (zonula ciliaris). / Posterior surface of lens 
 (lens crystallina). g Placed where some of the fibres of the suspensory liga- 
 ment are well seen uplifted from the grooves between the ciliary processes. 
 h Sclerotic (sclera). i Ridged and striated surface of the orbiculus ciliaris. 
 
PLATE 38 
 
 View of the interior of the anterior half of the globe of the eye of a full- 
 term foetus. 
 
 The retina is thick and fleshy looking ; at the margin of the ora serrata it 
 forms a rounded swollen edge. How far these appearances are due to post- 
 mortem changes or the influences of preservation is uncertain. At this stage 
 the vascularity of the retina is well displayed. Another feature of some 
 interest is that the zonule of Zinn is represented by but a narrow dark ring 
 round the lens. The ciliary processes, of which there are seventy-five, come 
 much nearer the circumference of the lens than in the adult. In this case the 
 posterior surface of the lens exhibits a four-fissured appearance. 
 
 a Sclerotic (sclera). b Thick retina (pars optica). c Orbiculus ciliaris. 
 d Corona ciliaris, made up of seventy-five ciliary processes. e Posterior 
 surface of lens (lens crystallina), with evidence of four fissures in its substance. 
 / Zonule of Zinn (zonula ciliaris), here seen as a narrow interval between the 
 circumference of the lens and the ciliary processes. g Swollen edge of pars 
 optica retinae where it forms the ora serrata. h Chorioid (chorioidea). 
 
PLATE 39 
 
 View of the interior of the anterior half of the globe of the eye. 
 Photographed by combined reflected and transmitted light. The cornea 
 and iris have been removed from the front of the lens. The zonule of Zinn is 
 seen as a light, faintly striated, annular zone surrounding the darker lens in the 
 centre of the preparation. The circumference of the lens displays an anterior 
 and posterior edge, to which are attached the fibres of the anterior and 
 posterior lamellae of the zonule of Zinn respectively ; these edges here and 
 there show the pointed attachments of the fibres of the suspensory ligament. 
 External to the zonule is the ring of the corona ciliaris, formed in this 
 specimen by eighty folds or ciliary processes. The orbiculus ciliaris is not 
 well seen, and the ora serrata is obscure. The vitreous has been removed, 
 but here and there patches of hyaloid membrane still remain attached to the 
 inner surface of the retina. 
 
 a Sclerotic (sclera). b Retina (pars optica). c Shows a patch of hyaloid 
 membrane attached to the retina. d Corona ciliaris, formed in this instance 
 by eighty ciliary processes, e Posterior surface of the lens, its circumference 
 marked by the attachment of the fibres of the ligament of the lens. / Ciliary 
 process (processus ciliaris). g Zonule of Zinn (zonula ciliaris), displaying the 
 fibres of the suspensory ligament of the lens. h Part of the orbiculus ciliaris 
 is here seen, i The chorioid (chorioidea) seen between the sclera and retina. 
 
PLATE 4O 
 
 View of the interior of the anterior half of the globe of the eye, taken by 
 reflected and transmitted light combined. The same specimen as PL 39. 
 
 In the centre is the lens, surrounded by a light finely striated zone, the 
 zonule of Zinn ; here the transmitted light shows up well the fibres of the 
 suspensory ligament (the cornea and iris have been removed from the front of 
 the lens). Wide of the zonule is the corona ciliaris, formed in this case by eighty 
 ciliary processes. External to the corona may be seen the orbiculus ciliaris (//), 
 and wide of that the general line of the ora serrata can be discerned, though 
 to some extent obscured by the vitreous and its hyaloid membrane (h). 
 
 a Retina (pars optica). b Sclerotic (sclera). c Vitreous and hyaloid 
 membrane. d Zonule of Zinn (zonula ciliaris), with the fibres of the suspen- 
 sory ligament passing from the ciliary body to the lens ; where they are attached 
 to the latter the capsule of the lens is here and there elevated and irregular. 
 e Ciliary process (processus ciliaris). f Posterior surface of the lens (lens 
 crystallina). g Corona ciliaris, made up of eighty ciliary processes sur- 
 rounding the zonule of Zinn. h Orbiculus ciliaris. *" Chorioid (chorioidea). 
 
PLATE 41 
 
 View of the interior of the anterior half of the globe of the eye, photo- 
 graphed by a combination of transmitted and reflected light. 
 
 This preparation is interesting because it displays an appearance not seen 
 in any of the other plates. Here, along the circumference of the lens, the lens 
 capsule is seen separated from the lens substance; or may it be the separation 
 of what Retzius calls the pericapsular membrane from the capsule itself? 
 
 a Chorioid (chorioidea). b Sclerotic (sclera). c Retina (pars optica). 
 d Separation of the layers investing the lens, either the lens capsule from the 
 lens, or the pericapsular membrane of Retzius from the capsule, e Posterior 
 surface of lens (lens crystallina). / Zonule of Zinn (zonula ciliaris), with the 
 fibres of the suspensory ligament faintly showing, g Corona ciliaris, made 
 up of eighty-four ciliary processes (processus ciliares). h Orbiculus ciliaris. 
 * Ora serrata, over which the hyaloid membrane may be seen in part 
 detached. 
 
PLATE 42 
 
 View of the interior of the anterior three-quarters of the globe of the eye 
 of an eighth-month foetus. The same specimen as PL 32. 
 
 The cornea and iris have been removed so that the specimen could be 
 photographed by a combination of reflected and transmitted light. The most 
 noticeable feature about this view is the redundancy of the retina ; how much 
 of this folding and puckering is due to post-mortem changes or the effects of 
 the reagents employed it is difficult to determine, but it may be pointed out 
 that it displays a transition stage between that represented in PL 17, the 
 eye. of a six and a half months' foetus, and that shown in PL 15, the eye of 
 a full-term foetus. 
 
 a Sclerotic (sclera). b Thick and folded retina. c Zonule of Zinn 
 (zonula ciliaris). The delicate radial fibres of the suspensory ligament of the 
 lens are revealed by the transmitted light : note that there is no unevenness 
 corresponding to their attachment to the circumference of the lens, d Ciliary 
 processes (processus ciliares), shown in shadow. e Lens (lens crystallina) : 
 its marked convexity is clearly indicated. / Chorioid (chorioidea). 
 
PLATE 43 
 
 View of the interior of the anterior half of the eye. 
 
 The vitreous and lens having been removed, the posterior chamber of the 
 aqueous chamber is laid open, and the posterior or uveal surface of the iris 
 is exposed. In the centre is the pupil, through which the cornea is seen with 
 the faint shadow of the pupillary margin cast on it. Wide of the iris the 
 corona ciliaris is seen, made up of seventy-seven ciliary processes. The 
 intervals between the largest folds seem tightly packed with smaller folds. 
 Outside the corona lies the orbiculus ciliaris, and external to that is the ora 
 serrata. Along the left edge of the preparation the retina is separated from 
 the chorioid. 
 
 a Sclerotic (sclera). b Remains of some of the vitreous and hyaloid still 
 attached to the retina. c Orbiculus ciliaris. d Corona ciliaris, made up of 
 seventy-seven ciliary processes (processus ciliares). e Pupillary aperture 
 (pupilla) : the posterior surface of the cornea is seen through it ; the pupillary 
 margin, very thin, is seen to be finely notched in correspondence with the 
 fine furrows and folds which are disposed on the posterior surface of the iris 
 in the pupillary zone. / Posterior or uveal surface of the iris. In a good 
 light this is seen to be traversed by radial folds converging to the pupil; 
 these are the structural folds of Schwalbe. g Retina (pars optica). h Ora 
 serrata. i Chorioid (chorioidea). 
 
PLATE 44 
 
 View of the interior of the anterior half of the eye, the vitreous and the 
 lens having been removed. 
 
 The posterior chamber of the aqueous chamber has thus been laid open. 
 A noteworthy feature of this specimen is the unpigmented condition of the 
 corona and orbiculus ciliaris. The uveal surface of the back of the iris is 
 deeply coloured. In the centre the aperture of the pupil is seen, through 
 which a shadow is cast on the concave inner surface of the cornea. Around 
 the pupil is the broad dark ring formed by the pigmented posterior surface 
 of the iris ; little or no detail of its structure can be seen. The corona ciliaris 
 lies external to this, made up of sixty-eight ciliary processes. Extending from 
 the corona to the ora serrata is the orbiculus ciliaris, the striated arrangement 
 of which is well displayed ; the more prominent fibres appear to pass from 
 the base of a ciliary process to one of the points which separate the lunules 
 of which the serrated edge of the ora is formed. In between these more 
 evident fibres, a number of parallel striae run forward to the edge of the 
 corona; a narrow, more lightly coloured zone appears just in front of the ora 
 serrata. 
 
 a Sclerotic (sclera). b Retina. c Chorioid (chorioidea). d Orbiculus 
 ciliaris. e Pupillary aperture (pupilla), through which is seen the posterior 
 surface of the cornea. / Uveal surface of posterior aspect of iris, g Corona 
 ciliaris, comprising sixty-eight ciliary processes (processus ciliares). h Ora 
 serrata. i Remains of vitreous and hyaloid membrane still adherent to 
 retina. 
 
PLATE 45 
 
 View of the posterior surface of the ciliary body and iris, detached from the 
 rest of the structures of the globe. 
 
 In the centre is the very dark pupil, surrounded by the slightly lighter 
 posterior uveal surface of the iris ; in a good light the radially arranged struc- 
 tural folds of Schwalbe are seen, replaced near the pupillary margin by a series 
 of fine folds the contraction folds of Schwalbe : this constitutes the pupillary 
 zone of Fuchs. It is this surface of the iris which forms the anterior wall of 
 the posterior chamber of the aqueous cavity. The corona ciliaris, made up of 
 seventy-one ciliary processes, forms the posterior circumferential boundary of 
 the posterior chamber. 
 
 The varying thickness of the ciliary body can be seen : thick where it is 
 cut near the outer edge of the corona, thinner where the section passes through 
 the orbiculus at some distance from the corona. Within the corona there 
 appear what seem to be some of the torn fibres of the zonule of Zinn the 
 suspensory ligament of the lens. 
 
 a Orbiculus ciliaris. b Corona ciliaris, formed of seventy-one ciliary pro- 
 cesses, c Ciliary zone of posterior or uveal surface of the iris : here are seen 
 the structural folds of Schwalbe. d Pupil (pupilla). e Pupillary zone of poste- 
 rior surface of the iris near the pupillary margin : here are seen a series of very 
 fine folds (contraction folds of Schwalbe). f Ciliary body, cut near the corona. 
 g The orbiculus, cut through where the tissue is thinner. 
 
PLATE 46 
 
 w 
 
 View of posterior surface of iris and ciliary body detached from the other 
 structures of the globe. 
 
 The ciliary processes and the orbiculus have been bleached by the action of 
 peroxide of hydrogen. This reagent does not appear to have removed the 
 pigment so completely from the posterior pigmented layer of the iris, for 
 here it is more dense. The arrangement of the folds on the posterior surface 
 of the iris is well seen. In the pupillary zone (c), near the pupillary margin, 
 the folds are fine and very numerous : these constitute the contraction folds 
 of Schwalbe. In the ciliary zone (d) the structural folds of Schwalbe are 
 seen radiating outwards and deepening towards the ciliary margin of the 
 iris. Here and there the uveal layer on the posterior surface of the iris is 
 injured and the lighter tissue beneath is seen. The corona ciliaris, made 
 up of seventy-one ciliary processes freed from their pigment, stands out clearly. 
 Fragments of the torn fibres of the suspensory ligament of the lens can here 
 and there be seen around the inner margin of the corona. 
 
 a Ciliary zone of posterior surface of iris with structural folds of Schwalbe. 
 b Pupil (pupilla). c Pupillary zone of posterior surface of iris with fine con- 
 traction folds. d Corona ciliaris, formed by seventy-one ciliary processes 
 (processus ciliares). 
 
PLATE 47 
 
 View of posterior surface of cornea, sclero-corneal junction, and internal 
 surface of anterior part of sclerotic. 
 
 The sulcus circularis corneae (b), around the scleral circumference of the 
 cornea, is well seen ; immediately outside it a narrow ring of unpigmented tissue 
 marks the position of the annular ligament (d), to which the ligamentum pec- 
 tinatum of the iris and the anterior insertion of the meridional fibres of the 
 ciliary muscle are attached. External to this the inner surface of the sclerotic 
 is exposed, with some of the pigmented tissue of the lamina fusca, which con- 
 nects it with the choroid, still attached. 
 
 a Sclerotic (sclera). b Sulcus circularis corneae. c Posterior surface 
 of cornea, forming the anterior wall of the anterior chamber ; here the posterior 
 lamina is wrinkled by the action of the preservative. d Torn surface of the 
 annular ligament (ligamentum annulare), to which the pectinate ligament 
 of the iris and the meridional fibres of the ciliary muscle are attached. 
 e Chorioidal surface of sclerotic, with remains ot the pigmented lamina fusca 
 attached. 
 
PLATE 48 
 
 View of the front of the lens, with the hyaloid membrane and fibres of the 
 suspensory ligament attached. 
 
 The preparation has been stained with picro-nigrosin, and photographed 
 by a combination of reflected and transmitted light. 
 
 The hyaloid membrane (a) when viewed in the stereoscope is seen to be 
 convex forwards around the lens ; but the lens indents its anterior surface and 
 lies in the fossa patellaris, to which it is adherent. The membrane displays 
 the impressions of the ciliary processes on its surface ; this is best seen above. 
 Radial striae also indicate the position of the fibres of the suspensory ligament 
 of the lens, which lie in contact with its anterior surface. These fibres (b) are 
 seen distinct and apart from the membrane on a plane anterior to it, and the 
 majority of them are clearly seen passing to be attached to the circumference 
 of the lens capsule near its anterior margin. 
 
 a Hyaloid membrane. b Fibres of suspensory ligament of the lens. The 
 space between a and b, close to the circumference of the lens, corresponds to 
 the so-called canal of Petit. c Anterior surface of lens. 
 
PLATE 49 
 
 Posterior view of lens, with the hyaloid membrane and fibres of the 
 suspensory ligament attached. Stained. The same specimen as Plate 48. 
 
 Wide of the lens the surface of the hyaloid membrane appears concave in 
 the stereoscope ; centrally it turns over the posterior surface of the lens, to the 
 capsule of which it is attached. In the centre, the hyaloid membrane, where it 
 forms the bottom of the fossa patellaris, is torn through and in part stripped off 
 from the posterior surface of the capsule of the lens. Arising from the posterior 
 surface of the hyaloid (viz. that towards the spectator) there are numerous 
 trabeculae which have been torn away from the vitreous substance. The 
 membrane bears the impressions of the ciliary process and also exhibits 
 a striated appearance ; faintly through the membrane and on a plane anterior 
 to it (i.e. farthest away from the spectator), here and there, the fibres of the 
 suspensory ligament of the lens can be seen. The space between the two near 
 the circumference of the lens corresponds to the so-called canal of Petit. 
 
 a Hyaloid membrane, with trabeculae attached to its near surface. b Indi- 
 cates a spot where the fibres of the suspensory ligament can be seen through 
 the hyaloid membrane lying on a plane anterior to it; i.e. on the far side 
 of the preparation. c Rent in the hyaloid membrane where it forms the 
 floor of the fossa patellaris ; the posterior surface of the capsule of the lens is 
 exposed through the opening. d Posterior surface of the lens, covered with 
 the hyaloid membrane. 
 
 H 
 
PLATE 5O 
 
 View of the posterior surface of the lens, with part of the hyaloid membrane 
 still attached. 
 
 The fibres of the suspensory ligament are clearly seen on the right side 
 of the specimen, which has been stained with picro-nigrosin and photographed 
 by reflected and transmitted light combined. This is the same specimen as 
 Plates 48 and 49. 
 
 The hyaloid membrane has been removed from the right side of the 
 preparation ; its ragged and torn edge is seen where it has been stripped off 
 from the posterior surface of the capsule of the lens, to which it is adherent. 
 In the stereoscope the fibres of the suspensory ligament of the lens are seen 
 distinctly in front of the upper torn edge of the hyaloid membrane. From the 
 near surface of the hyaloid membrane there are numerous ruptured trabeculae 
 passing ; these have been torn away from the substance of the vitreous. 
 
 a Hyaloid membrane. b Torn edge of the hyaloid membrane where it 
 forms the floor of the fossa patellaris, and where it has been stripped off from 
 the posterior surface of the capsule of the lens. c Posterior surface of lens 
 and capsule. d Fibres of the suspensory ligament attached to the circum- 
 ference of the lens capsule, mainly near its anterior border. 
 
Two views of the front of the lens, with part of the suspensory ligament 
 attached. 
 
 In both instances a ring of pigmented spots on the surface of the lens 
 marks the position of the pupillary margin ; in the lower preparation, due 
 possibly to post-mortem changes, there is a marked increase in the convexity 
 of the anterior surface of the lens, corresponding to the area circumscribed by 
 the pupillary margin. 
 
 In the lower specimen a portion of the ligament of the lens is seen. This, 
 at a distance of about 2 mm. from the circumference of the lens, is seen to 
 consist of a delicate transparent membrane, probably continuous posteriorly 
 with the inner stratum of the pars ciliaris retinae ; nearer the lens it breaks 
 up into a fine shredded membrane, the fibres of which are seen to be attached 
 in a nearly uniform line to the anterior portion of the circumference of the lens. 
 On comparing these specimens with the other photographs in which the 
 ligament of the lens is shown in situ, it will be seen that there is not that 
 depth and variation in the planes of attachment of the fibres of the zonula 
 which is so apparent in the other preparations ; here seemingly we have to 
 deal only with the anterior part of the zonule, the posterior portion having 
 been removed. This is further explained in Plates 49 and 52. 
 
 a A few scattered fibres of the suspensory ligament of the lens, seen 
 attached at b to the capsule of the lens. c Anterior surface of lens, with ring 
 of pigment spots marking the position of pupillary margin. d Anterior surface 
 of lens, showing a more marked convexity within the pigmented ring which 
 marks the position of the pupillary margin. Whether due to post-mortem 
 change or no, this appearance indicates that the iris can exercise some 
 restraining influence on the convexity of the lens. e Fine fibres of the 
 anterior portion of the suspensory ligament of the lens. These are seen to be 
 derived from the splitting up or shredding of a continuous membrane at/. 
 
 H 2 
 
PLATE 52 
 
 View of the lens, with parts of the suspensory ligament connected with it. 
 Upper specimen is the front of the lens, lower specimen the back. 
 
 The anterior surface of the lens, shown in the upper print, is marked by 
 a ring of pigment spots which indicates the position of the pupillary margin. 
 The posterior surface, represented in the lower figure, has slightly floccular 
 appearance as if something had been torn away from it. It is here that the 
 lens is in contact with the hyaloid membrane of the vitreous. Note particularly 
 that there are no indications of definite fibres having been torn away from the 
 posterior aspect of its circumference. The fibres attached in the anterior part 
 of the circumference form a very definite shredded sheet, the filaments of which 
 unite externally to form a delicate membrane, in all probability continuous 
 posteriorly with the internal stratum of the pars ciliaris retinae which overlies 
 the orbiculus and ciliary body. These are the fibres of the suspensory ligament 
 of the lens which lie in front of the so-called canal of Petit. 
 
 a Scattered fibres of the suspensory ligament of the lens, attached to the 
 front of the circumference of the capsule. b Anterior surface of the lens, with 
 pigment marks showing position of pupil. c Fine striated membrane which 
 becomes shredded nearer the lens (d), the fine isolated fibres being attached 
 very definitely to the front of the circumference of the capsule of the lens. 
 e Posterior surface of the lens ; this is seen to display a delicate floccular 
 appearance, due probably to its separation from the hyaloid membrane. It is 
 markedly more convex towards the centre. 
 
PLATE 53 
 
 Anterior view of half of lens, divided sagittally with part of suspensory liga- 
 ment attached. 
 
 The fibres here displayed are the strands of the zonule of Zinn. As will 
 be seen, the filaments are formed by the splitting up of a membrane (d} t the 
 shredded fibres of which pass to be attached to points on the capsule of the 
 lens occupying different planes around its circumference ; it is between these 
 strands that the so-called canal of Petit is placed. The specimen was stained 
 with picro-nigrosin. 
 
 a Cut edge of posterior surface of lens (lens crystallina). b Anterior sur- 
 face of lens. c Shredded fibres of the suspensory ligament of the lens, 
 forming the fibres of the zonule of Zinn. d Delicate membrane from which, 
 by the splitting of it up, these fibres are derived. This membrane is probably 
 in continuity with the internal stratum of the pars ciliaris retinae. 
 
PLATE 54 
 
 View, by transmitted light, of the front of the ciliary body, lens, and suspen- 
 sory ligament, separated from the other structures of the globe. 
 
 The specimen has been stained with picro-nigrosin so as to render more 
 distinct the fibres of the suspensory ligament. In the stereoscope the diver- 
 gence of the strands of the suspensory ligament as they pass to the circum- 
 ference of the lens can be made out distinctly ; the angular interval separating 
 them around the circumference of the lens forms the so-called canal of Petit. 
 
 a Scleral surface of ciliary body (corpus ciliare). b Lens (lens crystallina), 
 so deeply stained as to be opaque : note here and there on the circumference 
 the pointed attachments of the fibres of the ligament of the lens. c Fore part 
 of ciliary processes (processus ciliares). d Zonule of Zinn (zonula ciliaris) : 
 the fibres of the ligament of the lens are deeply stained, and show up well by 
 transmitted light. In the stereoscope it will be seen that the fibres are 
 arranged radially in different planes. Between them runs the so-called canal 
 of Petit around the circumference of the lens. 
 
PLATE 55 
 
 View, by transmitted light, of the back of the ciliary body, lens, and suspen- 
 sory ligament, separated from the other structures of the globe. 
 
 The specimen is the same as that represented on Plate 54, and has been 
 stained with picro-nigrosin so as to render more distinct the structure of the 
 zonule of Zinn. The shredded appearance of the ligament of the lens is well 
 displayed, and it will be apparent that all the fibres are not attached in the 
 same plane at the circumference of the lens. The interval around the circum- 
 ference of the lens between the anterior and posterior main zones of attach- 
 ment of these fibres is the so-called canal of Petit. At numerous points on 
 the circumference of the lens, the capsule of the lens exhibits traction effects 
 corresponding to the attachment of the fibres of the suspensory ligament. 
 
 a Zonule of Zinn (zonula ciliaris) : the fibres of the suspensory ligament are 
 seen radially arranged. As will be seen in the stereoscope, some of the fibres 
 lie in front of the others. The space between is the so-called canal of Petit. 
 b Lens (lens crystallina) : the points of attachment of some of the fibres of the 
 suspensory ligament are clearly indicated by elevated points on the circum- 
 ference of the lens. c Anterior extremities of the ciliary processes (pro- 
 cessus ciliares). d Inner surface of the ciliary body, here forming the corona 
 ciliaris. The details of the ciliary processes are not seen, owing to the fact 
 that the specimen has been photographed by transmitted light. 
 
PLATE 56 
 
 a 
 b 
 
 c 
 d 
 
 The ciliary body, zonule of Zinn, and the lens, separated from the other 
 structures of the eye, stained with van Gieson, and photographed from behind 
 by transmitted light. 
 
 In this specimen, in addition to the radial fibres of the zonule of Zinn, 
 which have been amply demonstrated in many of the other photographs, there 
 are very definite indications, particularly in the upper part of the zonule, of 
 fibres having a circular disposition. 
 
 a Placed where the circular fibres of the zonule of Zinn (zonula ciliaris) are 
 best displayed. b Zonule of Zinn, with the radial fibres of the suspensory 
 ligament of the lens. c Lens (lens crystallina). d The ciliary body (corpus 
 ciliare): the projection of the anterior ends of the ciliary processes (processus 
 ciliares) form the outer notched outline of the zonule of Zinn. 
 
PLATE 57 
 
 View of the lens, vitreous ; and parts of the retina and chorioid of the eye of 
 a six and a half months' foetus, removed from the specimen shown on PL 18. 
 
 The shrunken and distorted vitreous body, with its hyaloid membrane, is 
 well seen ; within it the anterior part of the hyaloid artery is clearly displayed, 
 passing towards the posterior surface of the lens and there breaking up into 
 a number of fine branches. The lens, which tends to be more spherical in 
 shape, is shown surrounded by a collar consisting of the pars ciliaris retinae 
 (marked in solid black) and the cut and everted edge of the anterior part of the 
 pars optica retinae. 
 
 a Shrunken vitreous body (humor vitreus), surrounded by its hyaloid mem- 
 brane, b Central hyaloid artery, which occupies the position of the hyaloid 
 canal (canalis hyaloideus) of the adult ; it may be seen splitting up into fine 
 branches to supply the posterior surface of the lens capsule. c lens. 
 d Ciliary body (corpus ciliare), in solid black. e Everted cut edge of the 
 fore part of the pars optica retinae. 
 
PLATE 58 
 
 CL 
 
 View of the interior of the posterior half of the globe of the eye of a child 
 two years old. The photograph was taken twenty minutes after the removal 
 of the eye for an accident. 
 
 The retina is translucent ; the optic disk and the macula lutea are seen ; 
 unfortunately, the specimen is not so oriented that the two lie on the same hori- 
 zontal plane. 
 
 The optic disk (papilla n. optici), which exhibits evidence of optic neuritis, 
 is seen with a circular lighter area in the centre, the porus opticus (b) ; the 
 light and shade do not reveal the physiological excavation (excavatio papillae 
 nervi optici), but the retinal vessels can be seen as two dark spots above and 
 below the porus opticus as they turn over the edge of the excavation. About 
 4 mm. from the centre of the porus opticus, to the outer side, a dark spot marks 
 the position of the fovea centralis (c), with the slightly darker yellow spot 
 (macula lutea) around it. 
 
 The retinal vessels are well displayed (d), the veins being darker than 
 the arteries. 
 
 a Chorioid (chorioidea). b Optic disk (papilla n. optici), with the porus 
 opticus in the centre ; immediately above and below this the retinal vessels can 
 be seen turning over the lip of the excavation. c Fovea centralis : within 
 a somewhat darker area, the yellow spot (macula lutea). d Retinal vessels ; 
 the veins are darker and slightly larger than the arteries. e Sclerotic (sclera). 
 / Retina (pars optica retinae). 
 
PLATE 59 
 
 a. 
 
 View of the interior of the posterior half of the globe of the eye of a child 
 two years old. 
 
 This is the same specimen as that represented on PI. 58, with this differ- 
 ence that the preparation has been subjected to the influence of formalin for 
 48 hours and then photographed. The retina is now opaque, and the retinal 
 vessels are less clearly seen. The optic disk, with the porus opticus in its 
 centre, is not so well defined ; around it, however, a ring of pigmented spots, 
 the chorioidal ring, is well shown immediately above it. The position of the 
 fovea centralis is marked by a recess with puckered and swollen edges round it. 
 
 a Chorioid (chorioidea). b Optic disk (papilla n. optici), with porus opticus 
 in the centre ; immediately above may be seen indications of the chorioidal 
 ring. c Fovea centralis, with puckered and swollen retina around it. d Re- 
 tinal vessels. e Sclerotic (sclera). / Retina (pars optica). 
 
PLATE 6O 
 
 View of the interior of the posterior half of the globe of the right eye of an 
 adult after fixing. 
 
 The optic disk (e) is seen with a well-marked excavation, the right edge of 
 which throws a shadow across the bottom of the hollow. Around the edge 
 the retinal vessels may be seen passing to their distribution ; about 4 mm. to the 
 outer or left side of the disk the fovea centralis is seen, immediately sur- 
 rounded by a lighter zone ; there is also a very faint indication of a lighter 
 annular zone about 1-5 mm. from the fovea. 
 
 a Sclerotic (sclera). b Chorioid (chorioidea). c Retina (pars optica). 
 d Fovea centralis, surrounded by a light ring due to the thickening of the 
 retina ; outside this there is a darker zone bounded by another lighter ring 
 about 1-5 mm. distant from the fovea. e Optic disk (papilla n. optici), with 
 a well-marked depression (excavatio papillae nervi optici), over the lip of which 
 the retinal vessels are seen running outwards. / Retinal vessels. 
 
PLATE 61 
 
 View of portion of the fundus of an adult eye fixed soon after death. 
 The optic disk is not very clearly defined ; a slight depression is seen in 
 its centre (e). About 4 mm. from the centre of the disk the fovea centralis is 
 seen above it and to the left (the two, of course, would lie very nearly in the 
 same horizontal plane if the preparation were in its right position). The fovea 
 here shows as a pit in the centre of an elevated zone of swollen retinal tissue ; 
 this appearance is probably post-mortem. 
 
 a Sclerotic (sclera). b Chorioid (chorioidea). c Fovea centralis, surrounded 
 by a swollen and thickened ring of retinal tissue. d Retina (pars optica). 
 e Optic disk, not very clearly defined, with a slight central depression ; the 
 retinal vessels are seen passing over the edge of the depression. / Retinal 
 vessels (vasa sanguinea retinae). 
 
PLATE 62 
 
 View of the interior of the posterior half of the globe of the eye in an 
 adult. 
 
 At c the optic disk is seen with the retinal vessels radiating from it ; extending 
 from it in a downward direction, and to the right, is a thickened and swollen 
 fold of retina ; in this, about 4 mm. from the centre of the optic disk, a little pit 
 is seen : this marks the position of the fovea centralis. Unfortunately, the 
 specimen is not correctly oriented ; if it had been, the fold would have extended 
 horizontally outwards from the disk. This fold, the so-called plica centralis, 
 is a very constant feature in eyes that are examined some time after death. 
 The configuration of the fold is remarkably alike in all such specimens examined, 
 and would suggest either a looser attachment of the retina in this particular 
 region or a texture more prone to the absorption of fluids. 
 
 a Retina (pars optica). b Sclerotic (sclera), with the chorioid attached to 
 its inner surface. c Optic disk (papilla nervi optici) : indications of a central 
 depression, with a thickened outer lip over which the retinal vessels are seen 
 passing. d Plica centralis : a post-mortem appearance, with the fovea centralis 
 close to the lead line. e Retinal vessels. 
 
PLATE 63 
 
 View of the interior of the posterior half of the globe of the eye of a full-term 
 foetus. Same eye as Plate 38. 
 
 The retina appears thick and fleshy ; here and there, more particularly 
 along the line of the retinal veins, it is thrown into prominent folds. In the 
 centre of the optic papilla (/) is seen the excavation, over the edges of which 
 the retinal vessels may be seen passing. Extending upwards from the optic 
 papilla (had the specimen been properly oriented it would have been almost 
 horizontally outwards) is a thick fold of characteristic form (see Pis. 3, 4, 62), 
 the plica centralis, due undoubtedly to post-mortem changes ; on this, at the 
 point d, is a recess, the fovea centralis, situated about 4 mm. from the centre of 
 the optic papilla. The vessels of the retina are well displayed (e), the veins 
 showing up thicker than the arteries. 
 
 a Sclerotic (sclera). b Chorioid (chorioidea). c Thick folds of swollen 
 retina, corresponding to the direction of some of the larger veins. d Fovea 
 centralis, on the surface of the plica centralis. e Retinal vessels. / Optic 
 papilla with optic recess or excavation. g Thick retina. 
 
PLATE 64 
 
 View of the interior of the posterior half of the sclerotic. 
 
 The contents of the globe of the eye having been removed, the supra- 
 chorioidal layer has been torn through, together with the lamina fusca ; a certain 
 amount of pigment derived from the latter, however, remains ; in this is outlined 
 the position and direction of the various vessels and nerves as they pass through 
 the peri-chorioidal space. 
 
 The entrance of the optic nerve is seen passing through the summit of 
 a gentle elevation. The central artery of the retina is seen with two companion 
 veins. 
 
 a Part of one of the long posterior ciliary arteries torn across anteriorly. 
 b One of the ciliary nerves. c The sclerotic (sclera), shown cut through. 
 d Entrance of optic nerve : within the nerve, in the centre, may be seen the 
 central artery ; to its right its two companion veins are seen. e Indicates the 
 impression of the ramifications of the venae vorticosae. / The impressions of 
 the short ciliary arteries. g One of the venae vorticosae piercing the 
 sclerotic (?) 
 
 A view of the surface of the sclerotic, covered with the choroid, is not 
 included, as it shows little of interest except the pigment layer of the retina 
 covering its internal surface. 
 
PLATE 65 
 
 View of the outer or scleral surface of the chorioid, photographed from the 
 same specimen as in Plate 13, showing the various zones of the chorioid as seen 
 from the outer side when the sclerotic is removed. 
 
 In front the ciliary body (a), behind that the outer surface of the orbiculus 
 ciliaris (b). At (c), the surface which overlies the line of the ora serrata of the 
 retina is seen, whilst behind the external surface of the vascular layer con- 
 taining the ramifications of the venae vorticosae is revealed. Overlying this, 
 the long ciliary nerves (e) are displayed running forwards to the ciliary body to 
 form a plexus, whilst one of the long posterior ciliary arteries is also visible (h). 
 
 In the removal of the sclerotic the pigmented lamina fusca and the supra- 
 chorioidal layer have been torn apart. 
 
 a Outer surface of ciliary body (corpus ciliare). b External surface of the 
 orbiculus ciliaris. c The nervous plexus (orbiculus gangliosus), formed by 
 the splitting up of the long ciliary nerves. d Overlies the position occupied 
 on the inner surface of the chorioid of the ora serrata of the retinae, e Long 
 ciliary nerves running forwards to form the orbiculus gangliosus. / Ramifi- 
 cations of the venae vorticosae. g Great vorticose vein. h Long posterior 
 ciliary artery (arteria ciliaris posterior longa). 
 
 1284 
 
PLATE 66 
 
 View of the scleral surface of a portion of the ciliary body separated from 
 its connexions; this has been dissected off from the left-hand side of the speci- 
 men shown in Plate 24. 
 
 The anterior margin, where the iris has been separated from its connexion 
 with the ciliary body, corresponds to the annular ligament (see Plates 24 and 
 25). Thinning posteriorly, the outer surface of the orbiculus ciliaris is seen (e), 
 whilst to the left of this the thin layers of the pars ciliaris retinae (c) are shown. 
 Where the orbiculus joins the ciliary body the ciliary nerves may be seen (a) 
 breaking up to form a plexus (orbiculus gangliosus), the fibres derived from 
 which enter the substance of the ciliary body. 
 
 a Ciliary nerves breaking up to form the orbiculus gangliosus. b Scleral 
 surface of ciliary body (corpus ciliare). c Pars ciliaris retinae. d Anterior 
 edge of ciliary body attached to the annular ligament at the sclero-corneal 
 junction ; from the inner surface of this margin the iris has been torn away. 
 e External or scleral surface of the orbiculus ciliare. 
 
PLATE 67 
 
 View of the inner (retinal) surface of the separated chorioid. 
 The retina has been peeled off from this surface, leaving its pigment layer 
 in greater part connected with the inner surface of the chorioid and ciliary 
 body. Over the greater part of the inner surface of the orbiculus ciliaris this 
 pigment layer has been stripped off, as if there it weVe more readily detachable 
 from the chorioid. The iris has been removed, and the free anterior edge of 
 the ciliary body corresponds to the divided annular ligament at the sclero- 
 corneal margin. The ramifications of the venae vorticosae are seen through 
 the thin chorio-capillary layer. 
 
 a Divided annular ligament (ligamentum annulare), which connects the 
 ciliary body anteriorly with the sclero-corneal circumference ; the iris has 
 been torn away from the inner side of this ligament. b Ciliary body (corpus 
 ciliare) in section. c Ciliary processes (processus ciliares). d Orbiculus 
 ciliaris. c Orbiculus ciliaris with the pigmented layer of the pars ciliaris 
 retinae stripped off. / Corresponds to the attachment of the ora serrata ; 
 here the pigment seems particularly thick. g Ramifications of the venae 
 vorticosae, showing through the chorio-capillary layer. // The inner surface 
 of the chorioid with much of the pigment layer of the retina attached. * The 
 chorioid (chorioidea) in section. 
 
INDEX 
 
 Angle, filtration, pp. 15, 33, 40. See also 
 
 Iridial angle. 
 
 iridial, see Filtration angle. 
 Annular ligament, 17, 32, 36, 40. 
 Anterior chamber, 14. See also Aqueous 
 
 chamber, anterior camera. 
 Aqueous chamber, 14, 30, 32, 34, 49. 
 
 - anterior camera of, 14, 32. 
 
 - posterior camera of, 15, 30, 34, 49. 
 Arteria centralis, 53. 
 
 retinae, 58. 
 Arteries, anterior ciliary, 36. 
 
 circulus iridis major, 55. 
 
 long posterior ciliary, 36, 40, 54, 55. 
 
 posterior ciliary, 54. 
 
 retinal, 58. 
 Artery, central, of retina, 53, 58. 
 
 hyaloid, 31, 52. 
 
 Calcar sclerae, 17. 
 Canal, hyaloid, 26, 48. 
 
 of Petit, 13, 28, 46, 48, 51. 
 
 of Schlemm, 17, 18, 32, 40, 41. 
 Capsule of lens, 57. 
 Chamber, aqueous, 14, 30, 32, 34, 49. 
 
 vitreous, 30. 
 
 Chorio-capillaris, n, 55, 56. 
 Chorioid (choroid), 10, 32, 41, 54, 55. 
 
 chorio-capillary layer of, n, 55, 56. 
 
 vascular lamina of, 53, 56. 
 Ciliary body, 8, 12, 32, 36. 
 
 folds, 41. 
 
 glands of Collins, 44, 49. 
 
 muscle, 13, 18, 36, 37, 40, 55, 61. 
 
 nerves, 36, 40, 55. 
 
 plexus, 36, 55. 
 
 processes, 10, 34, 36, 42, 47, 49. 
 
 processes, number of, 12, 41. 
 
 stomata, 34. 
 
 Circumlental space, TO, 12, 34, 41, 47, 48. 
 Colliculus nervi optici, 58, 60. 
 Collins, ciliary glands of, 44. 49. 
 
 Conjunctiva, scleral, 32. 
 
 Contraction folds of iris (Schwalbe), 35. 
 
 Cornea, 8, 32, 41. 
 
 measurements of, 8. 
 
 posterior limiting membrane of, 
 
 Corneae, sulcus circularis, 9, 16, 40. 
 Corneal aperture of sclera, 7. 
 Corona ciliaris, 12, 35, 36, 42. See also 
 Corona radiata. 
 
 radiata, 12, 47. See also Corona 
 ciliaris. 
 
 Crypts of iris, 34. 
 
 Descemet's membrane, 17, 41. 
 
 Filtration angle, 15, 33, 40. 
 Foetal eye, 8, 15, 38, 44. 
 
 - fovea centraiis of, 60. 
 
 - fundus of, 60. 
 
 - lens of, 46, 51. 
 Fontana, spaces of } 34. 
 
 Foramen opticum sclerae, 7, 21, 53, 57. 
 
 sclerae anterius, 7, 8. 
 Fossa patellaris, 26, 32, 49. 
 Fovea centralis, 21, 59, 60. 
 
 of foetal eye, 60. 
 
 Fuchs, concentric folds of, 35. 
 
 stomata of, 33. 
 Fundus oculi, 56. 
 
 of foetal eye, 60. 
 
 Glands, ciliary, of Collins, 44, 49. 
 
 H 
 
 Humour, vitreous, 22, 30. 
 Hyaloid artery, 31, 52. 
 
 canal, 26, 48. 
 
 fossa, 26, 31. See also Patellar 
 fossa. 
 
 membrane, 22, 30, 44, 48, 49, 52. 
 
INDEX 
 
 Iridial angle, see Filtration angle. 
 Iris, 13, 32. 
 
 concentric folds of, 33. 
 
 contraction folds of, 35. 
 crypts of, 34. 
 
 radial folds of, 33. 
 
 structural folds of (Schwalbe), 35. 
 
 K 
 
 Kuhnt, recesses of, 49. 
 
 Lamina basalis, n. 
 
 cribrosa, 7, 53, 57. 
 
 fusca, 8, 40, 53, 54. 
 
 suprachorioidalis, 8, 36, 54, 55. 
 
 vasculosa, u. 
 
 vitrea, n. 
 Lens, 25,34,38,45,49. 
 
 capsule of, 51. 
 
 equatorial region of, 27. 
 
 equatorial zone of, 29, 46, 47, 48. 
 
 foetal, 46, 51. 
 
 measurements of, 27. 
 
 nuclear part of, 27. 
 
 pericapsular membrane of (Ret- 
 zius), 46. 
 
 stars, 38, 45. 
 substantia corticalis, 27. 
 suspensory ligament of, 13, 26, 29, 
 34, 37, 47, 49. See also Zonule of 
 Zinn and Zonula ciliaris. 
 Ligament, annular, 17, 32, 36, 40. 
 pectinate, 17,32,40,41. 
 suspensory, of lens, 13, 26, 29, 34, 
 37, 47, 49. See also Zonule of Zinn. 
 Lymph space, perichorioidal, 53. 
 
 M 
 
 Macula lutea of retina, 21, 57, 59. 
 Membrana limitans ciliaris, 25. 
 Membrane, Descemet's, 17. 
 
 hyaloid, 22, 30, 44, 48, 49, 52. 
 
 pericapsular, of Retzius, 46. 
 pupillary, 15. 
 suprachorioidal, n, 40, 41, 53, 54. 
 
 See also Lamina suprachorioidalis. 
 Muscle, ciliary, 13, 18, 36, 37, 40, 55, 61. 
 
 N 
 
 Nerves, ciliary, 36, 40, 55. 
 
 ciliary plexus of, 36, 55. 
 Nervous tunic, see Retina. 
 
 O 
 
 Optic cup, 21, 58. 
 disk, 57. See Optic papilla, 
 nerve, colliculus of, 58. 
 papilla, 21, 57. 
 
 papilla, physiological cup of, 21, 58. 
 Ora serrata, 19, 20, 23, 44, 55. 
 Orbiculus ciliaris, 8, 10, 12, 36, 41, 47, 48, 
 5i, 55- 
 
 Pars ciliaris retinae, 19, 41, 51. 
 
 iridica retinae, 19, 25, 41, 45. 
 
 optica retinae, 19, 41, 44, 55. 
 Patellar fossa, 26, 31, 49. 
 Pectinate ligament, 17, 32, 40, 41. 
 Perichorioidal membrane, n. See also 
 Suprachorioidal membrane. 
 
 space, 8, 40, 41, 52, 54. 
 Petit, canal of, 13, 28, 46, 48, 51. 
 Physiological excavation or cup of optic 
 
 papilla, 21, 58. 
 
 Pigment layer of retina, 19, 25, 54, 56. 
 Plexus gangliosus ciliaris, 36, 55. 
 Plica centralis of retina, 22, 59. 
 Posterior camera of aqueous chamber, 
 15, 30, 34, 49. 
 
 limiting membrane of cornea, 
 
 17- 
 Post-lental space, 26, 31. 
 
 Process, scleral, 17. 
 
 Processes, ciliary, see Ciliary processes. 
 
 Pupillary margin, 33. 
 
 membrane, 15. 
 
 stomata, 33. 
 zone of iris, contraction folds of, 35. 
 
 Recesses of Kuhnt, 49. 
 Retina, 18, 44, 56. 
 
 foetal, 24, 45, 60. 
 
 fundus oculi, 56. 
 
 macula lutea, 21, 57, 59. 
 
 optic disk, 21, 57. See also Optic 
 papilla. 
 
INDEX 
 
 Retina, pigment layer of, 19, 25, 54, 56. 
 
 plica centralis, 22, 59. 
 veins of, 58. 
 
 vessels of foetal, 45. 
 
 yellow spot, 57, 59. See also Ma- 
 cula lutea. 
 Retinae, pars ciliaris, 19, 41, 51. 
 
 pars iridica, 19, 25, 41, 45. 
 
 pars optica, 19, 41, 44, 55. 
 Retinal vessels, 58. 
 Retzius, pericapsular membrane of, 46. 
 
 Schlemm, canal of, 17, 18, 32, 40, 41. 
 Schwalbe, contraction folds of iris, 35. 
 
 structural folds of iris, 35. 
 Sclera, 7, 32, 40, 53. 
 
 corneal aperture of, 7. 
 
 optic foramen of, 7, 53. 
 
 thickness of, 7. 
 Scleral conjunctiva, 32. 
 
 process, 17. 
 
 spur, 17. 
 Sclero-corneal junction, external, 10. 
 
 - internal, 10, 40. 
 Sclerotic, see Sclera. 
 Space, circumlental, 10, 12, 34, 41, 47, 48. 
 
 of Fontana, 34. 
 
 perichorioidal, 8, 40, 41, 52, 54. 
 
 post-lental, 26, 31. 
 
 Stomata of iris, 33. 
 
 ciliary, of iris, 34. 
 pupillary, of iris, 33. 
 Structural folds of Schwalbe, 35. 
 Sulcus circularis corneae, 9, 16, 40. 
 
 sclerae externus, 10. 
 Suprachorioidal membrane. 11, 40, 41, 
 
 53. 54- 
 
 Suspensory ligament of lens, 13, 26, 29, 
 34, 37, 47, 49. See also Zonule of 
 Zinn and Zonula ciliaris. 
 
 U 
 Uveal tract, 10, 41, 55. 
 
 Vascular coat of eyeball, 10. See also 
 
 Uveal tract. 
 
 Venae vorticosae, see Vorticose veins. 
 Vitreous humour, 22, 30, 48, 61. 
 Vorticose veins, 8, n, 36, 41, 54, 56. 
 
 Yellow spot, 21, 57, 59. See also Macula 
 
 lutea. 
 
 Z 
 Zonule of Zinn, 13, 26, 29, 34, 37, 46, 47, 
 
 49. See also Suspensory ligament 
 
 of lens. 
 Zonula ciliaris, see Zonule of Zinn. 
 
OXFORD : HORACE HART, M.A. 
 PRINTER TO THE UNIVERSITY