558 William Patten 



lated in weak sulphuric acid, their outer thirds are retained as thin and 

 transparent membranes, along wMch one may see several fine lines, un- 

 doubtedly the continuation of the nerve fibres, seen more distinetly on 

 cells prepared in other ways. The inner ends of these pigment cells end 

 in a rather blunt point, on which I bave not been able to distinguish 

 those root-like fibres, so common upon the inner ends of most epithelial 

 cells. But this very circumstance makes it much easier to follow those 

 nerve fibres, just described, through the basalmembraneinwards, 

 a considerable distance, until they are lost in the mass of scattered 

 fibres which supply the eye. 



It is difficult to obtain isolated retinophorae intact, and in a 

 condition to show the nerve endings. It is necessary to seach until a 

 good example is fonnd. The best way is maceration in y2o — Vao Vo 

 chromicacid, for ten or twelve days. The rods are somewhat shrunken 

 in the centre by this process, but are provided with a number of long 

 fibres, whose free ends project some distance beyond the inner edges of 

 the rods. These free ends are covered with a great number of fibrillae, 

 which brauch from the main fibre at right angles, and, projecting a 

 short distance, end ina minute, refractive globule (fig. 48). The fibres 

 may be foUowed along the outer surface of the rod, where they form a 

 complete network of distinct, longitudinal fibres, and small, irregularly 

 distributed, cross ones, or fibrillae. At the outer end of the rod, the 

 longitudinal fibres become continuous with each other by means of con- 

 necting loops, as I bave distinetly seen in several cases. The loops may 

 be distinguished from the other cross fibres, by their greater size and 

 distinctness (fig. 59) . It is very difficult to find retinophorae, treated 

 in this manner , which bave the rod stili attached, therefore it is not 

 possible to follow the nerve fibres along the whole length of the celi, 

 because they are so intimately united with the rods that, when the latter 

 are detached, the nerve fibres are carried with them. Yet I bave seen 

 the retinophorae with the rod stili attached, and bave followed the nerve 

 fibres almost down to the base of the cells. 



In sections, one can, under favorable circumstances, see a special 

 aggregation of nerve fibres, passing to each retinophora, and ascending 

 along the outer surface, between it and the inner pigment cells, until, 

 towards the outer ends of the latter, they disappear. It is therefore only 

 on macerated specimens, that I bave been able to follow the nerve fibres 

 over the surface of the rods, where they terminate as already described. 



The retinophorae are, moreover, supplied with a second form of 

 nerve fibres, which I believe to be characteristic of these structures, and 



