154 couES, 



ward for one-third of an inch ; becomes tendinous about the middle of 

 the forearm, passes behind the foot of tlie radius and over tlie in- 

 sertion of supinator longus, to spread into a broad fascial tendon, by 

 which it is finally inserted into the bases of the 2d, 3d and 4th 

 metacarpals. From its ver}^ high origin upon the humerus, this 

 muscle is the principal passive or indirect flexor of the hand when the 

 forearm is extended. 



Flexor carpi ulnaris. — While all the other muscles lying upon the 

 forearm, are in greater or less part condylar in origin, this arises 

 wholly from the ulna. It is a flat muscle, lying superficial upon the ulna 

 behind ; its posterior border corresponding to the edge of the bone 

 and arising therefrom in greatest part, but also having extensive 

 olecranar origin. It becomes tendinous near the wrist, and is in- 

 serted into the base of the 5th metacarpal, partaking somewhat of the 

 general tendency to aponeurotic expansion that characterizes all 

 the tendons coming down upon the back of the hand. As somewhat 

 of a corollary of the last statement, it may be here observed, that the 

 tendons along the back of the wrist and hand are pressed close to 

 the bones, while those upon the front of the wrist and the palm are 

 away from the bones, and are sepai'ated by deep distinct interstices of 

 areolar tissue containing much fat. 



The other muscles of the forearm all act upon digits, either sepa- 

 rately or in common. 



d. Acting upon digits. 



(a'. — From humerus or forearm.) 



There is only one digital flexor upon the front of the forearm. 

 The superficial or " perforatus " flexor is confined to the hand, as the 

 corresponding flexor of the toes is to the sole. Of extensoi's upon 

 the back of the forearm there are, besides the one common to the 

 fingers, two special ones for the thumb and little finger respectively. 



Flexor digitorum communis (profundus s. perforans). — Lies be- 

 tween the radial and ulnar extensores carpi ; a muscle of large size, 

 flattened shape, and somewhat complicated structure. It has exten- 

 sive origin, both from humerus and forearm bones. Its humeral ori- 

 gin corresponds with that of the extensor carpi radialis, but is a little 

 lower down upon the inner condyle and more external ; this part of 

 the muscle is larger than the other; it has aponeurotic investment 

 upon both sides, and mainly contributes to form the stout tendon 

 that runs someway up in its substance, and is thus, as it were, em- 

 braced by two muscular valves. The tendon flattens at the palm, in 

 a direction contrary to the flattening of the muscle above. The ulnar 

 portion of the muscle arises from all of the upper three-fourths of the 

 surface of the bone — excepting a small line along the ulnar ridge 

 which is occupied by the origin of extensor carpi ulnaris — up to the 



