53 



we shall then have two Flexors and two Extensors. The largest 

 I and most powerful of these tendons is that of the Perforans 

 muscle ; the next, that of the perforatus. The two last main- 

 tain a very intimate companionship from their origin to their 

 insertion. They are the two largest of the fore limb. The late 

 Professor Dick's favorite theory concerning the navicular dis- 

 ease was, that "injury to this tendon in the synovial capsule of 

 the navicular joint was most generally the primary and proxi- 

 mate cause." The perforans tendon passes under the navicu- 

 lar bone, and is inserted into the posterior pit of the pedal bone. 

 The navicular bone affords a fulcrum, by which means the 

 flexion of the foot is accomplished more easily than could be 

 done without any such fulcrum. 



REMARKABLE MECHANICAL ARRANGEMENTS. 



The merely mechanical arrangement governing the action of 

 the flexor tendons or sinews is of a very remarkable character ; 

 but I do not propose to enter into its consideration beyond its 

 immediate influence upon the motions of the foot. Both of 

 these tendons have the same origin, and, though their connec- 

 tion from their origin to their insertion is so intimate, they pre- 

 serve their individuality throughout their whole course to the 

 foot. Both of them have their accessories above and below the 

 the knee. The perforans is aided by the Ulnaris Accessorius 

 and the Radialis Accessorius above the knee, and a tendon 

 called the tendo-subcarpal below the knee. The perforatus de- 

 rives assistance from a ligament above the knee, called the 

 Superior Suspensory. At the back of the knee the perforans 

 clasps the perforatus in such a manner as to form a sheath, 

 through which the latter may glide ; and at the back of the fet- 

 lock joint the latter performs a similar office for the former. 

 Reaching the coronal bone, the perforatus divides itself into 

 two points of insertion, one going to the inner and the other to 

 the outer posterior edge of that bone. The perforans here be- 

 comes flat and thin, and adapts itself in width to the length of 

 the navicular bone, against which it presents a hard gliding 



