DE. J. MURIE ON THE FOEM AlfD STEUCTUEB OF THE MANATEE. 159 



the tendons of the primi internodii poUicis and h)ng supinator obliquely crossing it at 

 the wrist. 



An extensor communis digitorum has an origin, as usual, from the outer condyle and 

 ulna ; its well-developed muscular mass lies mesially in the forearm, filling the broad 

 hollow thereon. It becomes tendinous as it approaches the wrist, and divides into 

 four flat broadish slips, which proceed in an expanded manner to as many of the outer 

 digits. That to the third finger is rather the broadest and strongest ; and the two ulnar 

 tendons come off together somewhat higher than the radial ones. 



Differentiated from the last is an extensor minimi digiti, which, like it, is flat. 

 Springing chiefly from the radio-ulnar ligament of the joint, it runs at first below and 

 then alongside the communis digitorum. Its tendon occupies the groove on the radial 

 side of the ulna, and at the wiist splits into two, — the short, broad, stronger division 

 being inserted into the proximal end of the fifth metacarpal — the second, longer tendon 

 proceeding to the proximal phalanx of the same digit. 



An extensor carpi ulnaris springs from the back of the outer humeral condyle, at first 

 lying upon the pollicial extensor and then obliquely qn the surface of the ulna. Its 

 flat tendon widens as it courses round the outer distal ulnar extremity, and becomes 

 incorporated with the strong carpal aponeurosis. Its fibres, moreover, mingle with 

 those of the carpi radialis, whilst it finally has distinct insertions into the unciforme, os 

 magnum, and proximal end of the fifth metacarpal. 



There is barely a division between what appears to represent the extensor primi 

 and secundi internodii poUicis. The former may be differentiated as a flat, broadish- 

 based, lanceolate-shaped, fleshy muscle, which has origin in an oblique position along 

 three fourths of the shaft of the ulna. Its tendon, also broad, flat, and strong, passes 

 as usual in the styloid groove, and over that of the long radial extensor to be inserted 

 into the proximal end of the first metacarpal. The latter, secundi internodii pollicis, 

 has also a lanceolate (but much smaller) muscular belly, which fills the deepish 

 interosseous interval, and at the radial groove emits a tendon which joins deeply that 

 of the first-mentioned muscle. The difference in direction of the fleshy fibres dis- 

 tinguishes the above conjoined muscles. 



Ventral Surf ace = Flexors. — The biceps has a large, long inner muscular belly, and a 

 comparatively short, diminutive, chiefly tendinous outer belly. The first or main portion 

 of muscle arises by a short, but strong, tendon from the rudimentary coracoid process. 

 Proceeding over the insertions of the subscapularis and the conjoined tendon of the 

 teres major and latissimus dorsi, it is inserted by a flat oblique tendon into the lower 

 third of the inner side of the humeral shaft, on a level with the pectoralis major. 

 The second portion of the biceps springs from the outer or anterior border of the first 

 belly, and, with a short rounded thin muscular development (£^), ends in a narrow tendon. 

 The latter is continued to the radial tuberosity, but mingles with the infundibular or 



VOL. Yiii. — PART III. September, 1872. 2 b 



