34 THE SURGICAL ANATOMY OF THE HORSE 



visible. Behind the ligament is the perforans tendon, posterior to 

 which, again, we have the tendon of the superficial flexor of the digit. 

 Running down the whole length of the large metacarpal bone is the 

 tendon of the extensor pedis muscle. 



The lower extremity of the large metacarpal bone is observed to 

 articulate with the right sesamoid bone and the first phalanx, thus 

 forming the fetlock joint. The articular surface of the large metacarpal 

 is observed to be markedly convex from before to behind. The articular 

 surfaces of the suffraginis and the sesamoid bone are correspondingly 

 concave, the surface of the latter bone being in a manner complementary 

 to that of the suffraginis. In section the sesamoid bone here appears 

 elongated from above to below. Above it the suspensory ligament dis- 

 appears. This is due to the fact that the ligament has divided above the 

 joint and the outer division has passed to the outer side of the sesamoid. 



Sections of three ligamentous bands are observed to be attached to 

 the base of the sesamoid. They are the divisions of the inferior 

 sesamoidean ligament. The most superior runs to the upper extremity 

 of the back of the suffraginis ; the middle band runs to the same bone, 

 to which it is attached about half way down its posterior surface. The 

 remaining band is not attached to the suffraginis, but runs downwards 

 to the upper border of the complementary cartilage of the os coronas. 

 Closely applied to the back of the sesamoid bone is the perforans 

 tendon, behind which the perforatus is still placed. Between the latter 

 tendon and the skin of this region, is a considerable thickness of 

 fibro-fatty tissue. If the tendons be traced downwards, however, their 

 relationship to one another will be noticed to have altered, for the 

 perforans will be seen to pass along a groove in the perforatus, and 

 continue its course across the back of the navicular bone to its 

 attachment into the semilunar crest of the pedal bone. 



This groove in the perforatus is the outer half of the peculiar ring 

 which this tendon forms for the transmission of the perforans tendon. A 

 Httle lower down, the termination of the right half of the perforatus 



