THE VERTEBRATE EYE. 



121 



an image o^ a h c will be tlirown on a screen or on a 

 retina at a' h' c'. The image, it will be observed, is 

 necessarily reversed. This is the form of eye which 

 we possess ourselves : it is, in fact, a camera obscura. 

 It is that of all the higher animals, of most molluscs, 

 the ocelli of insects, etc. 



Fig. 77, taken from Helmholtz, ^Yill give an idea cf 

 the manner in which we see. 



Fig. 11. — (?, Vitreous liumor; L, lens; W, aqueous humor; c, ciliary process; d, 

 optic nerve ; e e, suspensory ligament ; k k, hyaloid membrane ; //, h h, cornea ; 

 g g, choroid; i, retina; 1 1, ciliary muscle; mf, nf, sclerotic coat; j^ P> iris; s, 

 the yellow spot. 



The eyeball is surrounded by a dense fibrous mem- 

 brane, the sclerotic coat, or icJiite of the eye, mf, nf, which 



