OF THE MUSCLES, 103 



Insertion of the perforatus tendon : which below the knee 

 is the posterior of the two. Into the sides of the os corona, 

 by a division of its substance. 



Insertion of the perforans tendon. Into the inferior and 

 posterior of the os pedis. These tendons, in their pro- 

 gress, receive two bands or accessory ligaments ; which 

 prevent them, when put on the stretch, distressing the 

 muscular fibre. The superior originates from the posterior 

 and inferior of the radius ; and goes to both the tendons. 

 The inferior comes from the bottom row of the knee bones, 

 and the head of the large metacarpal bones ; and goes almost 

 entirely to the perforans. 



There may also be seen above the knee ligamentous 

 bands, uniting the perforans to the perforatus. 



The perforans and perforatus tendons. The perforans 

 originates from the smallest muscular belly. After the two 

 have received the superior accessory ligament, they pass 

 through the synovial space at the back of the knee ; the 

 perforans here being grooved for the reception of the per- 

 foratus. Above the knee the perforans also receives the 

 tendons of the accessory flexors ; and thus, increased in 

 bulk, comes forth below the knee the most anterior of the 

 two ; the perforatus being semicircular for the protection of 

 the perforans. About the upper third of the large meta- 

 carpal bone the perforans receives the inferior ligament. 

 In this position the tendons journey to the fetlock joint ; 

 where the perforatus expands, and embraces the perforans 

 all round. The sheath thus formed is synovial within and 

 without. Without for gliding upon the sessamoid bones; and 

 within for the free passage of the perforans. This sheath is 

 continued a short distance, when the perforatus divides, 

 going to either side of the os corona. The perforans, after 

 it emerges from the sheath, proceeds above the elastic frog 

 to below the navicular bone, to be inserted into the sole of 

 the OS pedis. There is a synovial capsule between the 

 lower surface of the navicular bone and the upper surface 

 of the tendon ; the joint so formed being the seat of navicular 

 disease. 



Flexor ulnarius accessorius {Plate III. 12). Origin. 

 From the inner side and lower border of the ulna. Inserted. 

 Close to the trapezium, into the perforans, by long tendon. 



