DR. J. MURIE ON THE FORM AND STRUCTURE OF THE MANATEE, 159 
the tendons of the primi internodii pollicis and long supinator obliquely crossing it at 
the wrist. 
An eatensor 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 wrist 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 eatensor carpi ulnaris springs from the back of the outer humeral condyle,-at first 
lying upon the pollicial extensor and then obliquely on 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 pollicis. ‘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 Surface=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 (5), ends in a narrow tendon. 
The latter is continued to the radial tuberosity, but mingles with the infundibular or 
VOL. VIII.—PaRT 11, September, 1872. 2B 
