144 MUSCULAR SYSTEM. 



St7i(ctiire. — The superior attachments of the mass of muscle 

 (common to this and the perforans) are in part fleshy, but prin- 

 cipally tendinous : the tendinous part being underneath and 

 applied to the trochlea of the condyle, which in the motions of 

 the joint it plays over. The mass is divisible (more or less 

 completely) into three or four or more distinct portions, whose 

 surfaces are partly aponeurotic, and whose interiors (with the 

 exception of the one next the radius, which is commonly the 

 most completely separable) are intersected with layers of ten- 

 don. Just above the knee it contracts its substance and be- 

 comes tendinous, forming two flattened tendons which pass down 

 under the posterior annular ligaments. The posterior of these 

 tendons, the tendo perforatus, is neither so broad nor so flat as 

 the other ; it presents a concave surface anteriorly, to embrace 

 its companion in front. At the back of the fetlock joint, it ex- 

 pands so as more completely to cover the perforans, and sends 

 off a crescentic process which surrounds that tendon. At this 

 part also a tendinous theca includes both tendons, having at- 

 tachments on each side to the sesamoids. Opposite to the small 

 pastern joint, the perforatus splits into two divisions, having the 

 perforans passing between them : the triangular interval left is 

 occupied by a portion of membrane which is so attached as to 

 from a circumscribed synovial bag. 



Action. — To bend the fetlock and pastern joints ; and also to 

 assist in the flexion of the knee. 



FLEXOR PEDIS PERFORANS. — Epico)idj/lo-phaIa)igeus. 



Situation, form, and superior attachment. — The same as the 

 preceding. 



Inferior attachment, to the posterior concavity of the os pedis. 



Structure. — The fleshy origins and bellies of this muscle are 

 confounded with those of the perforatus. As they approach the 

 knee, however, they separate ; and then the perforans runs im- 

 mediately behind the perforatus. At the knee, like its fellow, it 

 is wholly tendinous, and here indeed partakes somewhat of the 

 nature of cartilage, as it passes through the same synovial bag- 

 as encloses its companion. Below the knee, these tendons as- 

 sume different shapes; the perforans being cylindroid, the other 

 flattened ; and this admits of the adaptation of their surfaces to 

 each other. In their passage down the leg, they are connected 

 together and invested by cellular tissue : a loose cellular sub- 

 stance also connects them to the suspensory ligament and 

 cannon bones. The perforans tendon at the back of the fetlock 

 spreads again in breadth, and re-assumes a cartilaginous texture, 

 and is likewise (the same as at the knee) surrounded by a syno- 



