EYE OF THE ENGLISH SPARROW 379 



with each other to form a complete network in this great vascu- 

 lar coat. The finer divisions and branches are too intricate to 

 show in such a figure. 



The pectinal artery (P) divides as it enters the optic nerve 

 tract. A better idea of the course of this artery can be had by 

 consulting figures 73, 74, and 75, plate 12, which are photo- 



Fig. 16 Posterior view of the eye of the sparrow after the sclera has been 

 removed to show the larger branches of the ciliary arteries and the artery and 

 vein of the pecten. Lc, long ciliary arteries which run forward parallel with the 

 long ciliary nerves; Op, optic nerve, showing its extension obliquely downward 

 and forward; P, artery to pecten; V, vein from pecten. X 10. 



graphs of sections at right angles to the pecten and vertical to 

 the retina. In figure 75 a cross-section of the artery is shown, 

 both in the angle of the optic nerve and eye on the outside, and 

 ahnost at the base of the pecten. In figure 74 the course of the 

 artery in its passage to the base of the pecten can be followed. 

 The veins carrying blood from the pecten emerge from the 

 lower or distal end of the optic disc (fig. 16, V). A more detailed 



