POSTERIOR MEMBER. 



285 



FIG. 94. 



the muscles experience less fatigue and contract to better advantage. 

 A short canon is less heavy, oscillates more freely, unfolds itself more, 

 and does not necessitate the same elevation of the 

 member above the ground to reach the limit of 

 its movements. Hence it is advisable to seek, 

 in the pendulum under examination, a great ex- 

 tent for the display of what we have already 

 designated its active function ; in its passive func- 

 tion the canon is inert, being incapable of accel- 

 erating or slackening the movement which is 

 communicated to it. (See Forearm and Leg.) 



Width and Thickness. The width of 

 the canon is measured from before to behind, 

 considering the animal in profile. It proceeds 

 from the separation of the principal bone of this 

 region from the flexor tendons of the phalanges, 

 which procured also to the latter the designation 

 well detached (Fig. 94). It is due, in the ante- 

 rior members, to the volume of the antibrachial 

 muscles ; in the posterior, to the width of the 

 hock, which carries the summit of the calcaneus more behind. In each 

 of the members it results, besides, from a more 

 or less marked prominence of the sesamoid 

 bones behind the fetlock articulation. 



Is it necessary to say now that this width 

 is an absolute quality for all kinds of services ? 

 Evidently not, since it is itself derived from 

 other good points which we have already de- 

 scribed, such as the volume of the muscles, the 

 width of the articulations, and the length of 

 the lever-arm. If, however, in theory, the 

 width of the canon in the anterior member 

 coincides generally with that of the fetlock, it is 

 possible, notwithstanding the development of the 

 latter, that the former may be deficient from ex- 

 cessive narrowness at its superior part. 



The flexor tendons, being then too strongly 

 tensed in the fold of the knee by the tarsal 

 sheath, descend obliquely upon the sesamoids 

 by gradually separating from the metatarsus, a 

 vice of conformation which renders the tendons weak, less effective 



FIG. 95. 



