326 H. M. BERNAED. 



which the meridians had a spiral twist. For a long time I 

 dismissed them as purely accidental phenomena, bat now 

 correlate them with the protomitomic filaments, as these 

 latter run outwards towards the rods. 



Figures showing* the same connections between the strias 

 and the nuclei might have been given also from other 

 mammalSj e. g. from the rat. But these thin mammalian rods 

 seem to have nothing like the number of fibrils running down 

 their outer limbs as can be seen on the thick rods of the 

 Amphibia (see Part II, Pis. 30 and 31), and their internal 

 axial reticulum is greatly reduced.^ 



We thus have the outermost fringe of the retinal pro- 

 tomitomic system running down the rods which are the 

 end organs of the retina as an organ of vision, while the 

 proximal fringe of the same system is continuous with the 

 nerve-fibrils. We are now able to give a diagram (fig. 22) 

 showing the protomitomic system forming the 

 bridge between the rods and the nerves for the 

 conduct of the stimuli. 



The diagram is not intended to represent the true con- 

 ditions, but only to illustrate the essential relations of the 

 parts. The nuclei, for instance, are drawn too far apart; in 

 very young eyes they may be tightly packed together (cf. 

 fig. 14), and, in most eyes, they remain fairly crowded except 

 in the innermost layer, which thins out first ; the middle layer 

 thins out only in very old eyes. On the right the two phases 

 of the nuclei, which Avill be discussed below, are indicated. 

 The syncytial strands other than those in the reticular layers 

 are not shown, nor is any attempt made to indicate the very 

 variable distribution of the granular cytoplasm. 



' The internal reticulum, reduced in very tliin rods lo little more than a 

 Ijiaiicliing axial thread, has been seen and pliotograplied by Dr. Lindsay 

 Johnson, who claimed it, as an axial nerve. This claim is apparently nearer 

 the truth than was the axial nerve or nerves of liiLter and Ilcnsen (see Part 

 11, p. ISO). 1 have, however, seen nothing that even appears to confirm Dr. 

 jjindsay Johnson's claim that these fibrils are continued beyond the rod (see 

 ' Areh. Ophlhal.,' New York [1896J, p. 450, fig. 26). 



