LESSON 96.] THE EYES IK MAMMALIA AND MAN. 



311 



this process continues until four arched vessels alone remain attached 

 to the inner circumference of the membrane, and finally these dis- 

 appear. 



1411. This membrane is sometimes (at a certain age) found at- 

 tached to the crystalline lens, and sometimes it is detached ; when 



FIG. 442. 



FIG. 441. 



Vessels of the arteria centralis 

 retina, human. 



Anterior capsule of the lens, human. 



FIG. 443. 



the latter occurs, it has been usual to .call it " membrana pupillaris " 

 it is in reality the anterior capsule of the lens. 



1412. The posterior capsule lies between the crystalline lens and 

 the vitreous humor. To perform its function, it requires to be vas- 

 cular, but from the peculiarity of its position it appears to be cut 

 off from all sources of supply. 



1413. The arteria centralis retina passes through the vitreous 

 humor, and having reached the 



posterior capsule, terminates in a 

 plexus of capillaries distributed 

 to that membrane, but which are 

 not nearly so numerous as those 

 of the anterior capsule ; they are 

 represented in Fig. 443 ; a is the 

 terminal portion of the arteria 

 centralis retina. 



1414. The vessels of the pos- 

 terior, like those of the anterior 

 capsule, are removed by absorp- 

 tion when their function has ceas- 



ed, and the lens fully formed ; it Posterior capsule of the lens. 



sometimes, but rarely, happens that they become permanent, and 



