270 THE RETINA. 



Having carefully examined the retina since these obser- 

 vations and views have been published, I have succeeded in 

 verifying the majority of the structures and relations described 

 by Mliller and Kolliker ; but cannot coincide with the latter 

 in opinion that the rods, cones, and Mlillerian filaments are 

 nervous structures. They have neither the general aspect 

 nor the anatomical relations of mere nervous textures. Each 

 rod or cone, with its Mlillerian filament extending inwards to 

 the limitary membrane, with the ovoidal bodies developed on 

 it, would appear referable rather to the class of structures to 

 which the touch-corpuscles and Pacinian bodies belong. 

 They are structures developed around the extremities of the 

 ultimate filaments of the optic nerve, for the purpose of 

 placing those extremities in the necessary position and cir- 

 cumstances for being impressed by the rays of light. The 

 ultimate nerve-filament enters the Miillerian stem of the rod 

 or cone as it passes through the white cellular layer. This 

 filament is probably, as has been stated, a radiation from one 

 of the grey cells, which if they be collectively connected to 

 all the rods and cones, as well as to the filaments of the optic 

 nerve, may safely be considered, as Kolliker has pointed out, 

 to be a retinal ganglion, intermediate between the sentient 

 points of the retina and the sensorium, as well as between the 

 corresponding points of its own and of the opposite eye. The 

 ultimate nerve-filament, as it enters the Miillerian stem 

 obliquely outwards, probably terminates towards or at the 

 extremity of the rod or cone, so as to have its transverse 

 section directed outwards at right angles to the axis of the 

 rod or cone. Let it now be assumed that a ray of light cannot 

 impress an ultimate optic filament, except it impinge upon 

 the free extremity in the axis that is, at right angles to the 

 transverse section ; and let it also be admitted, with Briicke 

 and Helmholtz, that it is by light reflected from the bottom 

 of the eye that vision is affected, then the theory of the retina 



