56 THE AMERICAN MONTHLY [Apr. 



course and follows the curve of the eye, at first being 

 wholly on the outside of the choroid but as it advances 

 it sinks itself into and through this coating until it en- 

 croaches upon the retina. Fig. IV., B. 



It continues until the equatorial diameter of the eye 

 is reached when it turns at a right angle and passes 

 directly across the eye just back of the lens where it 

 expands and becomes the inner layer of the retina. The 

 branch from the optic nerve which is known as the 

 complementary nerve, runs a short course to the back of 

 the eye where it divides and subdivides into numerous 

 branches which spread out on the outside of the choroid, 

 where in the vicinity of the equator of the eye they ap- • 

 pear to be distributed very evenly, as seen on cross- 

 section, in collections or bundles. The further divisions 

 may be traced to the pigmented epithelium of the ten- 

 tacular portion of the eye where they end in very small 

 corpuscular bodies from which exceedinly fine wavy 

 filaments extend to the individual pigmented cells. 

 Fig. III. Branches are also given off which penetrate 

 the choroid coat. This branch is evidently a nerve of 

 general sensation while joined with it back of the eye is 

 one of special sensation, or the optic nerve. 



The Retina. — Of special importance and interest is 

 the study of the retina. The ordinary methods of hard- 

 ening and staining do not well show the retina for the 

 picture is very much distorted, the rod and cone layer is 

 destroyed or lost to view, but by hardening in Osmic 

 Acid and taking special pains in the further manipula- 

 tions I have slides which are beautifully correct in all 

 the details. 



By this process the retina is shown to be composed 

 of three principal layers ; an internal nervous layer ; a 

 middle, nucleated spindle celled layer, and an external 

 club shaped, palisade-like layer. The internal border of 

 the retina as seen on polar sections of the eye is limited by 



