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A MANUAL OF VETERINARY PHYSIOLOGY 



tendon, drawing the sesamoids closer to their articulating surface 

 the more extended the fetlock becomes. Or the slip may be 

 considered in the light of an extension of the suspensory liga- 

 ment, in order to afford it increased surface of attachment. 

 The use of the slip, however, is not very evident, and we have 

 never seen it sprained, which is the best evidence that its share 

 is not very important. 



The suspensory ligament becomes sprained when the flexor 

 muscles tire, for the fetlock- joint is supported not only by the 

 suspensory ligament, but by both flexor tendons. Division of 

 the perforatus produces very little effect on the dropping of 

 the joint ; division of the perforans creates evident effect, but it 



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Fig. 196. — Effect of Experimental Division of the Suspensory Ligament 

 and Flexor Tendons on the Obliquity of the Pastern (Lishman).* 



1. Division of the suspensory ligament has caused the fetlock to drop a little. 



2. Division of the flexor perforatus tendon has caused slight sinking of the fetlock. 



3. Division of both flexors, perforatus and perforans tendons, brings the heel of the 



foot to the ground, and causes the toe to turn up. 

 The fetlock -joint does not come to the ground unless all the structures are divided. 



requires division of both flexors to bring the heel to the ground 

 (see Fig. 196, J). 



Pastern- Joint. — This joint, formed between the first and second 

 phalangeal bones, allows of limited flexion and extremely limited 

 extension. It is, in fact, specially arranged to act during ex- 

 tension as if the first and second phalanx were only one bone, 

 and that no joint existed between them. This function comes 

 into play when the body rotates over the foot on the ground — 

 i.e., during the period the body is passing from the position in 

 Fig. 194 to that in Fig. 195. When the limb passes the vertical, 

 the two bones, owing to the arrangement of their ligamentous 

 connections, move as one on the pedal articulation ; in other 



* These figures are copied from photographs published in the Veterinary 

 Record, August 22, 1908. 



