314 MANUAL OF EQUINE MEDICINE. 



CHOREA. 



Definition. — Chorea is a peculiar disorder characterized by 

 irregular clonic contractions of different muscles, especially 

 those of the posterior extremities. 



Nature and Etiology. — There is great doubt as to the 

 true nature of chorea. As in man, it is of more frequent 

 occurrence in the young, but though similar in many points 

 in the equine species, it nevertheless cannot be regarded as 

 strictly analogous with chorea in man. 



Hereditary predisposition is perhaps the chief cause of 

 chorea, though malhygienic conditions, overwork and ex- 

 haustion, may also act as exciting causes.* 



In the horse, chorea is only exceptionally the sequel of 

 other diseases, such, for example, as the specific fevers. 



Several theories have been propounded from time to time 

 to account for chorea. 



By some it is regarded as a purely functional disorder, 

 i.e., unassociated with any organic change. 



By others it is held to be due to some diseased condi- 

 tion of the blood, probably associated with rheumatism. 



In some instances, at any rate, organic changes have been 

 found after death. 



Stringhalt, an involuntary convulsive action of the muscles 

 of one or both hind-legs, occasionally afi'ecting the fore-legs, 

 may be regarded as a choreic aff'ection. 



Stringhalt probably depends upon some S]3ecial lesion 

 interfering with the functions of the nerves supplying the 

 afi'ected muscles, or of the spinal cord itself. 



* Mr. Williams, in his ' Principles of Veterinary Medicine,' says he' 

 has on record one instance where four young horses, the progeny of a 

 dam which was affected in the back, died from spinal paralysis before 

 they had attained the age of thirteen years. A fifth showed signs of 

 aggravated nervo-muscular disturbance. 



