26 OPHTHALMOLOGY FOR VETERINARIANS 



The center or nucleus is unstriated and becomes scle- 

 rosed as age advances. It is supported by the suspen- 

 sory ligament or zonule of Zinn. This ligament is com- 

 posed of homogeneous fibers, which arise from the 

 ciHary body anterior to the ora serrata and the ciliary 

 processes, and it is fused with the lens capsule near the 

 border. The space between the fibers as they diverge 

 is called the canal of Petit, and is triangular in shape 

 on transverse section. The capsule is similar in struc- 

 ture to the suspensory Hgament. The anterior capsule 

 has a layer of epithehal cells on the surface next the lens, 

 which become associated with the lens substance near 

 the zonular portion. The posterior capsule has no 

 epithelium. 



Like the cornea, the lens has no blood-vessels of its 

 own. It derives its nourishment from the ciliary proc- 

 esses. 



The vitreous is a gelatinous substance, perfectly 

 transparent and colorless. It fills the vitreous chamber, 

 or that portion of the globe posterior to the lens, and it 

 is enclosed in a delicate structure called the hyaloid 

 membrane. At the anterior portion is a depression in 

 which rests the lens. . 



The vitreous mass is composed of rounded and 

 branched cells. It is devoid of blood-vessels, and re- 

 ceives its nourishment from the uvea. In the center 

 is a small canal which serves as a lymphatic channel. 

 This, in fetal life, was traversed by the hyaloid artery 



