MAY, 1921. AMERICAN MARSUPIAL, C^NOLESTES OSGOOD. 43 



part. The fleshy divisions end abruptly and equally about one-third 

 of the distance from the olecranon to the carpus. The posterior division, 

 therefore is not longer than the anterior as it is in the opossum and the 

 tendon is shorter. 



Flexor digitorum sublimis. Origin by three heads in the septa of the 

 ulnar head of the profundus. These give rise to three distinct slips which 

 send their tendons loosely bound together until they reach the palm 

 where they pass beneath the annular ligament and insert ectad of the 

 large profundus tendons at the bases of the first phalanx of the second, 

 third, and fourth digits, respectively. Their tendons are slender and 

 practically of the same size throughout. From their point of origin a 

 short thick muscle with fibers running diagonally opposite those of the 

 ulnar head of the profundus extends to an origin from the caudad surface 

 of the inner humeral condyle and from the proximal edge of the glenoid 

 cavity of the ulna. Whether it may be one head of the sublimis is doubt- 

 ful. It is very distinct. 



Flexor digitorum profundus. Origin by four heads each of which 

 sends a distinct tendon to the palm where all unite in a thick flat tendi- 

 nous mass which occupies most of the palmar space. From this three 

 strong tendons radiate to the middle digits. Two others going to the 

 pollex and the fifth finger are much smaller and arise from the ectal 

 surface of the common tendon. The heads are as follows : 



1. Ulnar head. Origin on the flattened posterior surface of the 

 proximal two-thirds of the ulna from the olecranon at least to a point 

 opposite the neck of the radius. Its tendon is very large and strong, 

 rounded in its proximal part, slightly tapering toward its middle, and 

 flattening as it joins the outer side of the palmar tendinous mass. 



This is the largest fasciculus of the forearm, lying beneath the flexor 

 ulnaris and giving shape to the limb. 



2. The second head lies superficially next to the flexor carpi radialis 

 and connected with it in its proximal part by intermuscular septa. It is 

 similarly connected with the fourth head for a distance of nearly half its 

 fleshy extent. Its origin is from the inner condyle of the humerus entad 

 of that of the palmaris longus. Its tendon joins the common tendon ectad 

 of that of the third head, the two being approximately of equal size 

 and lying midway between the tendons of the first and fourth heads 

 which are much larger. 



3 . The third head is very distinct and wholly free but lies deeper than 

 the second and is not exposed until that is reflected. It lies between 

 the flexor ulnaris and the second head of the profundus together with the 

 conjoined part of the flexor radialis. Its origin is from the inner side 

 of the lip of the lesser sigmoid cavity of the ulna. Its small round tendon 



