NERVOUS CONSTITUENTS OF THE RETINA. 



253 



spirals, as far as to the boundary line between the inner and 

 the outer segments. If the latter have become detached whilst 

 still well preserved in perosmic acid, it may be observed that 

 fine fibrils which are continuous with the strise of the internal 

 segment project free from the end, forming a kind of basket by 



Fig. 355. 



Fig. 355. Rod and cone from the retina of Man, preserved in a two-per- 

 cent, solution of perosmic acid, to show the fine fibres of the surface, 

 and the different lengths of the internal segment. The outer seg- 

 ment of the cone is broken up into disks, which, however, are still 

 adherent to one another. . Magnified 1,000 diameters. 



which the outer segment was previously enclosed. In short, 

 it may be said that here, as in the cones, a fibrous investment 

 for the outer segment is formed from the striae of the inner 

 segment, and that this to some extent at least can be isolated. 

 It is possible also, notwithstanding their delicacy, to perceive 



