DISEASES OF THE HOCK. 



305 



the halts less abrupt, and more time has been given to the 

 cavalry recruit horse for the evolution of his natural powers, 

 the disease has much abated in prevalence." — (Percivall.) 



The hock described as " tied in below " is that form where 

 the head of the metatarsal and cuneiform bones are small com- 

 pared with the bones above. The cuneiform and metatarsal 

 bones are receivers of weight and distributors of concussion ; 

 their capability to the performance of those functions depends 

 upon their size and development, and upon the breadth of sur- 

 face they present. AVhen not well developed, one cannot fail 

 to see the apphcability of the argument that they are predis- 

 posed to spavin, and as a rule practice proves its correctness ; 

 but there are many exceptions, and one often sees a badly- 

 formed hock remaining sound under very severe tests. 



The theory of Goodsir, that the motion of the true hock- 

 joint is like a screw, is well worthy of consideration. I have, 

 by the kindness of Professor Turner, obtained the loan of a 

 cast of several astragali united together, illustrative of the 

 screw-like direction of its articulating surface. The cast was 

 prepared by Mr. Stirling, the curator of the Edinburgh Univer- 

 sity Anatomical Museum, under Professor Goodsir^s immediate 

 superintendence. Being the result of the observations of one 

 to whom the Edinburgh Veterinary College is so especially 

 indebted, it cannot fail to be interesting. 



Fig. 51. — Astragali united to show the screw lines. 



By carefully examining the oblique pulley-like prominences, 

 and the deep groove between them, on the superior articulating 



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