194 LAMENESS OF THE HORSE 



The liock is kept fixed in position by the gastrocnemius and 

 the superficial digital flexor (perforatus). The latter structure, 

 which is chiefly tendinous, originates in tlie supracondyloid fossa 

 of the femur and has an insertion to the summit of the fibular 

 tarsal (calcis) bone. It relieves the gastrocnemius of muscular 

 strain during weight bearing. 



Smith^ styles the function of the stifle and hock joints a re- 

 cijirocating action, and we quote from this authority the follow- 

 ing: 



From Avhat has been said, it is evident that flexion and ex- 

 tension of stifle and hock are identical in their action. When 

 the stifle is extended, the hock is automatically extended, nor 

 can it nnder any circumstances flex without the previous flexion 

 of the stifle. There is no parallel to this in the body. The two 

 joints, though far apart, act as one, and they are locked by the 

 drawing up of the patella, and in no other way. The so-called 

 dislocation of the stifle in the horse is a misnomer. That the 

 patella is capable of being dislocated is beyond doubt, but the 

 ordinary condition described under that term, when the stifle 

 and hock are rigid while the foot is turned back with its wall 

 on the ground, is nothing more than spasm of the muscles which 

 keeps the patella drawn np. The moment they relax the pre- 

 viously immovable limb and useless foot have their function 

 restored as if by magic, but are immediately thrown out of gear 

 in the course of a few" minutes as a recurrence of the tetanus of 

 the petallar muscle takes place. The fascia of the thigh, like 

 that of the arm, is a most potent factor in giving assistance to 

 the constant strain imposed on the muscles of the limbs during 

 standing. 



Below the hock the hind liml) is arranged like that of the fore, 

 the deei5 flexor (perforans) receiving its additional support from 

 the "check ligament," as in the fore leg. 



The natural attitude of standing adopted by the horse is to 

 rest on three legs — one hind and two fore. If he is alert, he 

 stands on all four limbs; but if standing in the ordinary man- 

 ner, he always rests on one hind leg. He does not remain long 

 in this position witliout changing to the other. Hour by hour 

 he stands, shifting his weight at intervals from one to the other 

 hind leg, and resting its fellow by flexing the hock and standing 

 on the toe. He never spares his fore-limbs in this manner in a 

 state of health, ])ut always stands squarely on them. 



1 Manual of Velerinai-y Physiology, page 601. 



