566 DR. J. MURIE ON THE ANATOMY OF THE SEA-LION. 
impelling the body forwards in a watery medium. It also causes the encased flippers, 
along with their tendino-fascial expansions, to strike the ground in a clumping manner 
during progression on land. But the deep and superficial flexor tendons of the manus, 
here in one plane and not superimposed on one another, have, besides their synchronous 
action, powers more or less independent of each other; that is to say, the tendinous 
distribution does not influence each digit alike. First, then, the main tendon of the 
pollex is considerably stronger than the others, though not equal in size to its opposed 
enormous extensor on the dorsal surface. Flexion of the phalanges of the thumb on 
the metacarpal bone is supplemented by the broad and strong. tendinous ligament con- 
tinued on from the deep palmar fascia to the proximal end of the distal phalanx. The 
extra inner pollicial tendon, which is inserted into the root of the first phalanx, more- 
over helps to flex the enlarged thumb; and the action of the tendons, besides their 
bending movement, has somewhat of a pronating character. This latter oblique change 
of force appears to render assistance to the extensive ligamentous sheet of the palmaris 
secundus muscle inserted all along the margin of the first metacarpal and phalangeal 
bone; thus the combined action of the tendons of the flexor longus pollicis with it, 
doubtless produce that tilting inclination and consequent curvilinear angle or feathering 
of the flipper when swimming. Secondly, the tendinous slips of the flexor profundus 
are the chief flexors of the second and third digits, the pollicial division to the second 
digit in part representing the perforatus. Lastly, the multiple divisions of the sublimis 
are benders of the fourth and fifth digits, and partially so of the third. The high 
branching and tangential direction of the tendon to the fifth digit, besides flexion, gives 
it a slight divaricating power, which may be useful in walking on all fours or for 
natatory purposes. 
No development of a pronator quadratus is appreciable, the narrow, but immensely 
strong, interosseous ligament taking its place as a binding hinge of the radius upon 
the ulna. 
There is a well-developed flexor brevis minimi digiti (fig. 23, F.b.m.d). Its origin is 
from the outermost ulnar border of the ligamentous palmar fascia, from the tendon of 
the flexor carpi ulnaris, and from the pisiform bone; it is inserted by a broad tendon 
into the distal end and ulnar side of the fifth metacarpal. 
Abductor minimi digiti—What appears to represent this muscle is a short, strongish, 
broad band of fibres arising from between the fourth and fifth digits and from the deep 
palmar ligamentous fascia (A4d.m.d). It is inserted into the radial side of the fifth digit 
at the metacarpo-phalangeal articulation. 
Lumbricales with muscular bellies are absent; but it is possible that the extra dimi- 
nutive slips of tendon which are given off from the flexor profundus may be lumbrical 
remnants. 
Interossei—In the manus of the Sea-lion these muscles are well defined, full-bellied, 
and fleshy. As in some groups of a higher order (the Lemuride for example), besides 
