THE EYES OF AMBLYOPSIS. 



139 



It breaks up into smaller vessels distributed in the choroid. A vessel is usually found 

 in a groove of the pigment layer of the retina. This groove extends along the dorsal 

 wall of the eye otherwise it might be taken for the choroid fissure (fig. 50, cps.). 

 A somewhat larger vessel than at other points is found near the iris, where this 

 structure appears to be continuous with a deep choroidal groove (fig. 51 a, cps.). In 

 the young a blood-vessel enters the hyaloid cavity at this point. 



chr. 



chr. 



~ sd. c. 



nil. 



The eye itself, exclusive of choroid 

 and sclera, differs greatly both in size and 

 inner structure although the general ar- 

 rangement of the retinal cells remains the 

 same in all cases. In some cases the pig- 

 mrnt layer of the retina forms a large mem- 

 branous bag many times too large for the 

 inclosed structures which lie as a small 

 ball in this comparatively vast cavity. In 

 such eyes found in old individuals the 

 wall in many places is free from pigment. 

 In general the pigmentation of the retina 

 varies inversely as the pigmentation of 

 the choroid. In other individuals the eye 

 forms a compact mass of cells (fig. 53). 

 To anticipate somewhat, the vitreous 

 cavity with the hyaloid membrane and 

 its blood-vessels have entirely disappeared, 

 the ganglionic cells have in large part been brought together into a solid mass, 

 and the irideal opening has usually become closed. 



Pigmentcd Layer and Cones. - - The pigment cells as they appear in the best 

 preparations of the better-developed eyes may be described first (fig. 50). The 

 cells are longest near the entrance of the optic nerve. They possess an outer seg- 

 ment, not determinable in all cells, which is free from pigment. They have a homo- 



FlG. 51. From Amblyopsis 05 mm. long killed in Picric 

 Acid and stained with a Mixture of Ha?malum and 

 Indigo Carmine. Figures made with Bausch and Lomb 

 ^a Immersion and 4 Eyepiece. 



(a) Section of Right Eye. Choroida! Groove with one of 

 Scleral Cartilages in front of Eye. Nuclear Layers 

 thinner than usual. Densely Pigmented Segments of 

 Pigment Cells form a Conspicuous Layer just below 

 Pigment Nuclei. 



(6) Next Section after 51 a, showing Group of Elongate 

 Uveal Cells. 



