588 William Patten 



cluced to a single layer, extending as far as the thin wall of the om- 

 mateal sac, where the fìbres from the axial branch of the optic iierve 

 enter the retina. These cells are drawn out into two long fibres, which, 

 instead of penetrating the deeper parts of the retina, form an irregulär 

 layer of superficial, circular fibres. By isolating the entire retina and ex- 

 amining it from above, the large, ovai nuclei will be seen and the Pro- 

 longation of the spindle-shaped cells may be followed a short distance 

 (PI. 29, fig. 32 d). Toward the centre of the retina, the cells grow large 

 and round, until transformed into those of the outer, ganglionic layer. 



The inner ganglionic layer is composed of a single row of very 

 small, flattened cells, which, when seen at ali, were mistaken by pre- 

 vious writers for the nuclei of the retinophorae. This mistake is readily 

 made, since the small cells, almost completely filled with a flattened and 

 deeply stained nucleus, are squeezed fiat betweeu the walls of the retino- 

 phorae. The best method of studying them is by teasing macerated 

 eyes; the minute cells in question will then be seen closely attached to 

 the side of the retinophorae, — near the angle formed by their bent, 

 inner ends, — by means of several (6 or 7) radiating arms, which, ad- 

 hering closely to the wall of the celi, extend nearly parallel to each 

 other, towards the rods (PI. 29, fig. 38). On the outer side, one or two 

 large fibres extend towards the lens and become continued into the gang- 

 lionic branch of the optic nerve (PI. 32, fig. 140 ^c^). Thus the enlarged, 

 inner ends of the retinophorae are surrounded by innulnerable, longi- 

 tudinal fibres, which extend beyond the cells to the inner ends of the 

 rods, over the surface of which they form a network of fibres. One will 

 often be struck with the difficulty of separating these ganglionic cells 

 from the retinophorae, the reason being that the outgrowths of the cells 

 are provided with innumerable, lateral branches completely surrounding 

 the retinophorae with a network of closely united fibrillae, which prob- 

 ably penetrate the celi wall. When one has finally succeeded in isolat- 

 ing them, either by prolonged maceration, or by persistent tapping upon 

 the cover glass, many of the fibrillae will be seen stili attached to the 

 fibrous prolongations of the cells (PI. 29, fig. 36 y). There are, more- 

 over, many nerves arising from the outer layer of ganglionic cells and 

 continued directly onwards to the rods, while others, breaking up into 

 numerous smaller fibres, terminate in the walls of the retinophorae. The 

 nerves terminate in two ways. In the first method, which rarely occurs, 

 a single fibre impinges directly upon the celi wall and there divides into 

 several short fibrillae, connected at their distai extremities with a cir- 

 cular fibril enclosing the wbole (PI. 29, fig. 36 x] . In the second method, 



