XIIL] THE FROG. i$g 



c. Put on a high power and examine, make out 



the following points 



a. The internal limiting membrane, a thin struc- 

 tureless layer. 

 ft. The nerve-fibre layer: thin and granular. 



[Both a and /3 are often difficult to make out in 

 retinas prepared as above.] 



y. The nerve-cell layer: composed mainly of cells 

 like those described above (g. i. a), but rather 

 smaller than those from the sympathetic 

 ganglia. From some, branches can be traced 

 into the next layer. 



8. The molecular layer: this is thicker than any 

 of the preceding, and has a finely punctated 

 appearance : running through it the fibres of 

 Miiller (h. i. t) are very plainly seen. 



c. The inner granular layer: this is the layer 

 which usually looks clearest in sections, its 

 elements being less closely packed than those 

 of the other layers. It is made up of a num- 

 ber of nuclei (which in chromic-acid speci- 

 mens look granular), around which is col- 

 lected a very small amount of protoplasm, 

 and of fine fibres, some of which can be 

 traced joining the nuclei or granules. 



. The inter-granular (fenestrated} layer. A nar- 

 row cloudy layer in which no definite struc- 

 tural elements are visible. 



17. The outer granular layer. Much thinner than 

 the inner granular layer and more closely 

 packed. It is composed of distinct fibres 



172 



