DISEASES OF THE HIGHER SENSE ORGANS 427 



Lesions of the cornea are very frequent in all domestic 

 animals, as are their sequelae, anterior synechiae, prolapse of the 

 iris, opacities and scars (at any rate in dogs) ; in dogs and 

 horses superficial and deep inflammations and ulcers are also 

 common. Fistula and staphyloma follow as in man, as the 

 result of perforation. New growths, pterygium and dermoids 

 are not infrequent in horses, dogs and sheep. 



The various forms of inflammation of the conjunctiva from 

 simple catarrh to purulent (blenorrhagic) or diphtheritic con- 

 junctivitis, appear with the same symptoms as in man. Blenor- 

 rhagic inflammation is often most extensive in cattle, sheep and 

 dogs ; the diphtheritic form is confined to fowls, pigeons and 

 other birds, in which primary diphtheria of the throat and nose 

 has occurred. 



Diseases of the membrana nictitans are peculiar to animals ; 

 wounds occur in horses, cattle and dogs ; chronic inflammation, 

 accompanied by thickening, in dogs and swine; fibromata in the 

 larger animals, and prolapse in dogs and swine. 



Coloboma also occurs in animals, as a result of disturbances 

 in the normal formation of the fcetal pupil ; the pupil may be 

 closed either by posterior synechiae, or by swelling of the uvea. 

 Inflammation of the iris is very frequent, either primary or 

 secondary, to disease of the ciliary body or choroid. 



The causes of acute inflammation of the iris are either trau- 

 matism or infection. Iritis often extends to the ciliary body 

 and choroid, and if primarily infective it may lead to a general 

 purulent inflammation of the eye (panophthalmitis). 



Night blindness in horses is rather different from that in 

 man ; in man it is due to a decrease in central vision, conditioned 

 by a rapid contraction of the visual field when the light is 

 deficient, without any internal inflammation of the eye. In the 

 horse it is due to a periodically recurrent irido-choroiditis of 

 an infectious character, leading to destruction of the retina and 

 blindness in one or both eyes. 



As in children so in young domestic animals (dogs and 

 horses) opacity of the lens may occur as a congenital defect. 

 Cataract generally, however, occurs later both in these and in 

 other animals (bears, hyaenas, wolves, the smaller felidae, and 

 other small beasts of prey) ; it is the result of metabolic dis- 



