116 ANIMAL MECHANISM. 



point of vision. Nothing, however, is more absurd; 

 vision includes considerable surface. In the centre of 

 the substance of the nerve, an artery penetrates the eye, 

 accompanying the Jilaments, to nourish the humors. 

 When the cornea has been cut away, and the iris detach- 

 ed, this vessel may be distinguished, of a bright scarlet, 

 spreading its hair-like branches about, like the limbs of 

 a tree. The nerves which give sensation to the eye, 

 connecting it with the system, may be noticed, as previ- 

 ously remarked, lying between the two first coats. The 

 optic nerve conveys to the mind the sensation of the ex- 

 istence of things, as perceived by the eye, while the 

 commands of the same mind are conveyed to it by these 

 little threads of nerves, so insignificant, as to be often 

 overlooked in a dissection made purposely for them. 

 FIG. 9. 



Explanation of Figure 9. 



In this figure, the cornea is cut away, and the sclerotic dissected 

 back. This is a beautiful and easily accomplished dissection. In a 

 bullock's eye all these delicate nerves can be readily displayed. A 

 pair of sharp pointed scissors and a few pins, to hold parts to a board, 

 are the proper instruments. Even in schools, ladies could exhibit 

 most of this beautiful optical apparatus. 



