VETERINARY OPHTHALMOLOGY. 



115 



as a whole, it is divided into a nucleus and a cortex. 

 A single layer of fibers under the mici-oscope will be 

 seen to lie parallel and each measure about ^j^Vxr of an 

 inch in thickness. They, unite with each other by 

 serrated borders, by dovetailing. The lens acts as any 

 plus lens, bringing light to a focus. Cataract is the 

 common result of internal'ophthalmia and is an opacity 



Fig. 61. 



Fig. 62. 



of the crystalline caused by interference with its 

 nutrition. Ergotism is a cause, but we don't know how. 

 Cataract may occur at any age. Sometimes congenital. 

 Two principal divisions, hard and soft catai'act. 

 There is a peculiar form called morgagnian, and is 

 a hard nucleus or a fluid cortex, or a cataractous lens 

 floating in a fluid medium. Traumatic cataract is 

 a soft cataract following trauma. The detection of 

 cataract is by oblique illumination. The extraction of 

 the cataract will not improve vision, and as its appear- 



