450 H. M. BERNARD. 



ferred to above) that the outer limbs of the cones are also 

 striated will be discussed later. 



The Contents of the Rods. — According to Max 

 Schultze the outer limbs of the rods are built up of discs 

 joined together by some cementing substance. This descrip- 

 tion, propounded by so great an observer, seems to have had 

 the effect of turning away attention from Hensen's figures of 

 cross-sections of rods of the frog,^ which clearly showed some 

 definite internal structure. It must, however, be admitted 

 that Hensen's cross-sections differed among themselves; 

 there were two kinds (see PI. 30, figs. 1 , a, b, which reproduce 

 them), and they were not easy to reconcile with one anothei'. 

 Nevertheless I think it cannot be doubted that the discs of 

 Max Schultze, which are, I believe, artificial phenomena, 

 helped to consign them to temporary oblivion. As a matter 

 of fact, Hensen's figures, which were optical sections and 

 hence hazy, come near the truth, and are, as we shall see 

 presently, reconcilable with my own observations. It seems 

 faii'ly clear, for instance, that his two sections may compare 

 with my own figs. 9, b, 13, g, and 12, 13, h, respectively. 

 Hensen, however, was too anxious to discover nerve-endings, 

 and was therefore prepared to see fibrils in any clear space 

 or small refractive portion of the section. In the case of 

 fig. 7, a, he thought the meshes of the reticulum round the 

 periphery of the sections were fibrils of doubtful significance, 

 but in fig. 7, b, those in the centre were regarded as nerves, — 

 three, he thought, in the centre of each rod. 



With regard to the contents of the inner limb of the rod, 

 its most conspicuous element, the " ellipsoid," has long been 

 known ; it has been regarded as the organ in which the 

 nerves end (cf. fig. 23, on the right), and deserves a separate 

 section. This is readily accorded, inasmuch as it admits of 

 being described separately, and what follows will be clearer if 

 we temporarily ignore it. At the same time we shall find it 

 necessary to discuss the contents of both outer and inner 

 limbs together, passing by for the present this particular body. 



• Virchow's ' Arch. path. Anat.,' Bd. xxxix, 1867, pi. xii, figs. 7 and 8. 



