ORGANS OF THE BODY. 



t>41 



complete maze (B, g) of the most delicate nerve fibrillae (Schultze, Steinlin, 

 Hasse), which, there is every reason to believe, spring from the bipolar 

 cells of the internal granular layer and from the ganglion cells. 



(7.) The stratum cellulosum, or layer of the ganglion corpuscles, is the 

 next in order. It lies next the inner surface of preceding layer, but is 

 indistinctly marked off against the latter. Its pale, delicate, membraneless 

 cells (fig. 586, 587, 6 ; 596, B, h) are of different sizes, and may measure, 

 when particularly large, 0-0377 mm. in diameter. They belong, partly at 

 least, to the multipolar class, like those of the brain and spinal cord, and 

 appear also to possess a fibrillated structure ( 179, fig. 308). It is pro- 

 bable, also, that their ramifications have the same relations here as in the 

 nervous centres. One of them directed inwards, the axis-cylinder pro- 

 cess (fig. 596, B, h') appears to be continuous with one of the horizontal 

 optic fibres (i) of the stra- 

 tum fibrillosum (Corti, Re- 

 mak, Koelliker, H. Muller, 

 Schultze, Hasse, and others), 

 while protoplasm processes, 

 on the other hand, are given off 

 externally (g\ and it is sup- 

 posed undergo repeated sub- 

 division here, forming in the 

 delicate spongy tissue of -the 

 molecular layer a tangle of 

 the most delicate, and pro- 

 bably varicose filaments. 



Finally, commissural pro- 

 cesses have been stated to 

 exist between adjacent gan- 

 glion cells ( Corti, Koelliker) ; 

 but this has lately been again 

 questioned by many. 



The depth of the stratum, 

 cellulosum (figs. 586 and 

 587, 6) varies in the most 

 interesting way, according to 

 locality. It is greatest op- 

 posite the yellow spot, where 

 several rows of cells, some- 

 times from 6 to 10, may be 

 observed lying one over the 

 other. Here it may present 

 a thickness of 0'0999 mm., 

 except in the fovea centralis, 

 where it is much less. With 

 the distance from the macula 

 lutea the ganglionic layer 

 decreases more and more in 

 depth, until but two rows of 

 cells are to be seen, and then gradually one alone. In the vicinity of the 

 ora serrata, finally, the ganglionic corpuscles are only met with singly, and 

 with an ever-increasing interval between them. 



In the middle portion of the retina the quantity of sustentacular con- 



Fig. 596. 



