372 BOVINE PATHOLOGY. 



together to form the cornea proliferate freely and cause 

 opacity. 



Opacity op the Cornea also depends upon nutritive 

 conditions, and sometimes upon pressure, due to swelling 

 of the contents of the eyeball. Under these circumstances 

 it is temporary, and disappears with its cause, but when 

 it results from blows or other injuries, and sometimes after 

 ophthalmia, it may be permanent. When a slight bluish 

 imperfect opacity it is termed nebula, if more circum- 

 scribed, perfect, and with well-defined outlines, it is termed 

 albugo. These conditions are incurable ; they may become 

 less marked with time, and the process of diminution in 

 size may be accelerated by the application of caustic 

 agents, such as nitrate of silver. Cartwright describes it 

 in some cases, as due to plethora and the pendent position 

 of the head (^ Edinburgh Veterinary Review,' vol. v, 

 p. 22) ; but it probably is more frequently dependent on 

 defective nutrition. 



Staphyloma is either a tumour on the cornea or pro- 

 trusion of the lining membrane of the aqueous chamber 

 with its contents through an ulceration of the cornea. 

 Such ulcerations result from debility, especially that due 



Fig. 71. — Staphyloma. (Arraatage.) 



to defective assimilation of tissue formers, or occasionally, 

 perhaps, from ophthalmic corneitis. The projection is 

 opaque and generally irregular on the surface,' and in the 

 ulcerative form there is a tendency to evacuation of the 

 contents of the aqueous chamber. Ulcerations of the 

 cornea and tumours on it may be touched with nitrate of 



