530 Types and Market Classes of Live Stock 



contracted feet predispose the horse to navicular disease. In this way 

 the disease may be hereditary, as these predisposing causes may be 

 transmitted to offspring. High knee action, fast work, and hard pave- 

 ments also endanger a horse from this disease. Dry stables, heavy 

 pulling, and bad shoeing also tend toward the development of this 

 trouble. In the early stages of navicular disease, the animal at rest 

 points the affected foot forward and rests it on the toe, with the fet- 

 lock and knee flexed. In the lameness which develops, the affected 

 leg takes a short stride, and the toe strikes the ground first. The 

 disease is progressive and incurable, rendering the animal practically 

 valueless, but not entirely useless on soft ground. To relieve the 

 pain, neurotomy may be performed, an operation in which the sense 

 of feeling is destroyed in the foot by cutting out pieces of the nerve 

 at the fetlock. Navicular disease is one of the most serious un- 

 soundnesses. 



Periodic ophthalmia or moonblindness is a disease affecting the 

 eyes of horses, probably caused by a germ. It is quite commonly 

 called "moonblindness," because it was thought at one time that the 

 moon had some influence on the cause of the disease. There is un- 

 doubtedly an hereditary predisposition to the disease, but there are 

 few cases to indicate that the disease itself is transmitted from parent 

 to offspring, but rather the foal is born with a weakness of the eyes, 

 transmitted by the stallion or dam. Other predisposing factors are 

 low, swampy pastures, poorly ventilated or insufficiently lighted stables, 

 over-feeding, etc. 



The disease comes on with an inflammation usually of one eye. 

 The transparent portion of the eyeball becomes bluish or white in color, 

 most noticeable in the lower part. The eye is kept half closed on 

 account of pain produced by light. Often this is associated by a swell- 

 ing of the eyelids and reddening of the membrane lining them, with a 

 discharge of tears over the face. There is no indication of an injury 

 or more severe inflammation at one point than at another. In one to 

 two weeks these symptoms disappear and the eye may be practically 

 normal to all general appearances for a period of usually one to three 

 months, when another attack occurs more severe than the first. After 

 a few attacks have come and gone, the eye has a bluish appearance, 

 looks cloudy instead of clear, the eyeball is shrunken, retracted in the 

 orbit, and the lens develops a cataract. After having destroyed one 

 eye, the disease frequently affects the other, and the history of the first 

 is repeated. 



Poll evil is a fistula upon the poll of the head, and in no sense 

 differs from fistulous withers except in location. It is caused by blows, 

 bruises, and chafing by the halter or bridle. 



