THE EYE. 379 



anatomy of the retina must still be left in abeyance. The 

 radiating fibres either actually terminate in the filaments 

 observed by me on the surface of the expansion of the optic 

 nerve, or they are continuous with the true fibres of that 

 nerve, or at any rate are in connexion with them. In a 

 physiological point of view the latter supposition would, in any 

 case, be the most plausible ; and in support of it, it may be 

 stated, that in the true fibrous bundles of the retina, together 

 with the varicose nerve-tubules (fig. 303 3 ' a, b), there are fibres 

 of another sort (fig. 303 3 ' c), which, although of equal size, 

 agree in all respects with the radiating fibres in the absence of 

 varicosities, and in their less straight or more serpentine and 

 irregular course. It may be that these fibres are the direct 

 continuations of the horizontal terminal processes of the 

 radiating fibres, which subsequently, in their further progress 

 towards the optic nerve, acquire more and more of the character 

 of common nerve-tubules, and follow a more direct course. 

 However interesting this notion may be, according to which 

 the " rods" would be the terminations of the optic fibres, the 

 considerable difficulties attending it must not be concealed; 

 among which not the least is the circumstance, that, although 

 the "rods" and "cones" are certainly fifty times more numerous 

 than the fibres of the optic nerve, yet the radiating fibres 

 arising from the former, on their passage into the optic fibres, 

 subdivide, and, as it must probably be assumed, are continuous 

 with several of them — a difficulty, which might indeed be 

 removed on the hypothesis, that a single optic fibre receives or 

 gives off numerous radiating fibres, but is nevertheless of 

 such a kind that I do not consider it advisable to proceed 

 any further upon a basis unsupported by facts. 



In spite of the obscurity which, from what precedes, still 

 hangs over a very important point in the anatomy of the retina, 

 physiology may nevertheless even at present draw some useful 

 conclusions from the facts in our possession. In the first 

 place, since the demonstration by H. Muller and myself of its 

 connexion with the radiating fibre-system and the " granules," 

 the bacillar layer appears in quite a different light from that 

 in which it was previously held, and it is now obviously 

 impossible to regard it, with Briicke, as a catoptric, reflecting 

 apparatus. I look upon the " rods" and " cones," which may 



