ORGANS OF THE BODY. 



631 



tion, best seen near the lens. These were discovered by Henle. They am 

 some of them very fine, some stronger, as though made up of bundles of 

 the first, and are often connected together in a retiform manner. In many 

 points this membrane resembles certain kinds of connective-tissue, although 

 we are unable to discover at the nodal parts the usual nucleus of the con- 

 nective-tissue corpuscle. The fibres resist also, with great obstinacy, the 

 action both of alkalies and acids. 



314. 



The retina of the eye consists primarily of an expansion of the optic 

 nerve; but, besides this, it contains other form-elements of various kinds, 

 presenting a very complex structure. The extraordinary delicacy of this 

 membrane, combined with its liability to rapid decomposition, render it 

 one of the most difficult objects of histological investigation. For this 

 reason the controversies, in regard to its structure, are still far from being 

 set at rest, in spite of very extensive and thorough study, aided by the 

 discovery of the action of chromic, and later of osmic acids, on such 

 tissues. 



Of the later observers who have largely added to our knowledge of the 

 structure of the retina, H. Mutter deserves to be first mentioned. More 



Fig. 586. Fig. 587. 



Vertical sections of the human retina. Fig. 586, half an inch from the entrance of the 

 optic nerve. Fig. 587, close to the latter. 1, layer of the rods and cones (columnar 

 layer), bounded underneath by the membrana limitans externa; 2, external granular 

 layer; 3, intergrannlar layer; 4, internal granular layer; 5, molecular layer ; 6. layer 

 of the ganglion cells; 7, expansion of optic fiores ; 8, sustentacular fibres of Muller; 

 9, their attachment to the membrana limitans inlerna ; 10, the latter. 



recently still, the master-mind of Max Schultze has swept away many of the 

 difficulties which hung about this subject, on which he was justly regarded 

 as the highest authority at the time of his lamented death, which took 

 place on the 16th of January 1874. 

 41 



