372 SPECIAL HISTOLOGY. 



often more or less ventricose, which, gradually diminishing 

 in size, passes into a common "rod" without a point, and of 

 a shorter inner portion, somewhat constricted from the other 

 by a slight incurvation, in which an elongated or pyriform, 

 more opaque and brilliant body, 0002 — O'OOS'" in length, is 

 enclosed. On the internal aspect, these "cones," in which I 

 can see nothing but a cell with a nucleus, are, like the " rods," 

 continued into the succeeding layers of the retina, where we 

 shall again have to consider them, by fine filaments, 0*0004 — 

 00006'" in size, similar to those of the " rods." 



The "rods" and "cones" are arranged vertically upon the 

 retina, like palisades, in close apposition, and consequently, one 

 of their ends is directed towards the choroid and the other 

 towards the granular layer. Close to the macula lutea the 

 " cones" form an almost continuous stratum (fig. 304 2 ), so Jjiat 

 the " rods" are placed only in single series between them, but 

 more anteriorly they are wider apart, the distance between 

 them at first being about 0*002 — 0003'", and in the anterior 

 portions of the retina even 00004— 0*005"' (fig. 304 3 ), thus 

 affording room for more " rods" in the interspaces. Viewed 

 from without, the bacillar layer, when its 

 outermost surface is brought into focus, 

 exhibits rounded spaces, placed at a greater 

 or less depth, filled with a clear substance, 

 which also occupies elsewhere the inter- 

 stices between the elements of this layer. 

 These clear spaces, corresponding to the 

 "cones," present an internal, dark, smaller 

 circle, the terminal surface or apparent transverse section of 

 the "rod" which is seated upon the "cone," and are sur- 

 rounded by the closely crowded terminal surfaces of the " proper 

 rods," disposed in a sort of mosaic manner, their outlines being 

 indicated by the single, double, or multiple series of reticulations 

 (fig. 304). 



2. The granular layer, stratum granulosum (fig. 303 h,f), is 

 composed of opaque, granular corpuscles, reflecting the light 



Fig. 304. Bacilllar layer from without. 1, at the "yellow spot" (only "cones") ; 

 2, at the border of the same ; 3, from the middle of the retina ; a, "cones," or va- 

 cuities corresponding with them; b, "rods" of the "cones," whose terminal surface 

 is often placed rather more deeply than that of the proper "rods," c; x 350 diam. 



