274 THE MODERN HORSE DOCTOR. 



then, is on the inside of the hock, in the region of the tarsal 

 bones, and beneath the true joint, from which point it may both 

 spread and acquire magnitude. Hypertrophy, or enlargement 

 of the bone beneath the tarsal articulations, occurring on the up- 

 per part of the canon, does not constitute spavin : in England, 

 such an enlargement is denominated "a jack." 



As regards the Cause of Spavin. — From what has preceded, 

 the reader will see that it has two origins : 1. Hereditary. 

 2. Exciting. 



1. Hereditary Predisposition. — Facts have proved conclu- 

 sively that spavin, as well as predisposition — morbid tendency — 

 to the same, is transmitted from parents to offspring. It is prob- 

 able, however, that predisposition is more frequently transmitted 

 than actual disease ; for the latter does not make its appearance 

 so early as it otherwise would were it transmissible. Spavin is 

 not peculiar to colthood, but to adult life, and even then can often 

 be traced partly to an exciting cause — strain, injury, over-work, 

 &c. Predisposition may not always have an hereditary origin ; 

 still it will not differ in its mode of action from the former ; for 

 all predisposing causes produce in the economy certain changes 

 which may be said to prepare it for disease ; and, therefore, pre- 

 disposition, whatever its source, may be considered as the incu- 

 bative stage of disease. 



2. Exciting Causes are those from which this disease seems 

 to have direct origin — such, for example, as strain, injury, over- 

 work, &c. ; yet these fail to produce spavin in a great majority 

 of cases ; in confirmation of which we have only to look into the 

 history of our truck horses, particularly those use4 for several 

 years in the shafts. The herculean strength necessary to back a 

 load which requires the united strength of two or three to draw 

 would, one would think, be likely to produce spavin ; yet a great 

 proportion of such are exempt from this disease ; therefore we 

 may infer that exciting causes are in some cases inoperative, un- 

 less conjoined with predisposition. 



Symptoms of Spavin. — Unfortunately for the poor brute, 

 lameness is not generally of that character which incapacitates 

 him for work ; and thus he is urged to the performance of his 

 duties, the disease progressing, and his sufferings increasing, 



