LESSON 95.] THE EYES IN REPTILES, BIRDS, ETC. 



305 



FIG. 431. 



Eye of Emys Europcea. 



The crystalline lens (g) has a compressed FIG. 432. 



elliptical form, and a smaller axis than 

 the vitreous humor (h). The retina 

 terminates with a thickened edge at the 

 beginning of the cil- 

 iary processes, and a 

 similar structure is 

 presented in most of 

 the Chelonian rep- 

 tiles. 



1387. In the 



Snapping Turtle, the middle coat of the choroid presents a magnifi- 

 cent spectacle, when its vessels have been minutely injected, a figure 

 of which is given (Fig. 433), copied from a preparation. 



1388. The posterior part of the choroid, it will be seen, is pierced 

 for the transmission of the optic nerve (a) ; it is called the foramen 

 of Soemmering. 



1389. It will be seen that the vessels at this part are very mi- 

 nute, and that they gradually and steadily increase in size to the 

 anterior portion, just below the ciliary processes. At this point they 

 assume a very beautiful arrangement, and one that is peculiar, as 

 compared with other choroids. 



FIG. 433. FIG. 434. 



Choroid coat of the eye, Snapping Turtle. 



20 



Ciliary processes, Snapping Turtle. 



