9 Sept,, 1907.] 



Lameness in H orses. 



5^5 



experienced when tlje foot comes to the gronnd. Towards tlie termina- 

 tion of the act of bending the hock there is a noticeable " click " of the 

 joint', the last part of the act being sudden and swift. While the first 

 part of the flexion is directly due to muscular action, the latter part is 

 mechanical, the impetus gi\en by the muscular effort being, on account of 



Fit 



87. — Bones of hock, front view. Fig. 88. Bones of hock, back view. 

 (After Hayes.) (After Hayes.) 



the screw-like shape of the astragalus bone, continued until the joint is 

 bent to its limit ; in other words, the commencement of the movement is 

 effected by muscular effort, and its completion is effected by momentum. 

 The final jerk or click, so plainly observable in horses with extreme hock 

 action, produces a vibratory jar on the small bones of the hock such as 



Fig. 89. Comparison of spavined and nornal hocks. (After Hayes.) 



is not experienced in the knee or any other joint. Hence arises, it mav 

 be conjectured, the particular liability of the part to an inflammation, the 

 result of Avhich is the union of the bones and their consequent strengthen 

 ing to a degree capable of withstanding jar and concussion. 



