432 DR. J. MURIE ON THE ANATOMY OF THE WALRUS. 
the right side; 14 inch further on, the left subclavian splits into a large ascending 
branch, and a main trunk is carried on towards the axilla. The upper suprascapular 
and equally wide transverse cervical have, all things considered, great calibre, needful to 
supply the vast muscles clothing the neck. 
Comparing the vessels derived from the arch of the aorta in the Phocide and 
Otariide with those of the Trichechide, I find that the two former have three great 
trunks springing from the arch, whereas the latter has four. In the common Seal and 
the Sea-lion the short, wide innominate gives off the right carotid, which in the 
Walrus comes from the summit of the arch itself, in near proximity, however, to the 
innominata. 
The distribution of the arteries of the forearm in the Walrus have been both figured 
and described by Von Baer’, Those observed by me were much in accordance with the 
diagrammatic view he gives. The axillary, a wide stem, gives off a large subscapular 
and derivative circumflex branches. One or two arteries leave the brachial below the 
_neck of the humerus, and are distributed partly to the triceps, passing beneath the 
internal anconeus to the elbow-joint and muscles on the ulnar side of the forearm. 
These with other twigs doubtless are homologous with the superior and inferior pro- 
funda and the ulnar anastomotic. Dipping deeply in the lower humeral groove the 
brachial goes under the brachialis anticus muscle, and on reaching the forearm splits 
into several branches; but a main radial and lesser ulnar are perceived. Von Baer 
distinguishes a deep artery with several anostomotic branches and loops (which I take 
to be the anterior interosseous), and to the radial side of the radial trunk a long, but 
narrow, vessel which runs to the wrist parallel with it. These latter I did not dissect 
with care, though, from what I saw, I believe our specimen possessed similar peculiarities. 
His ramus volaris and ramus dorsalis I noted, and moreover examined the delta-like 
superficial palmar arch, which freely communicates by many twigs with the deeper 
arterial distribution. The second, third, and fourth interdigital spaces have forked 
branchlets, and the first a single one, chiefly supplying the ulnar side of the pollex. 
Among noteworthy points in the vascular distribution of the fore limb of the Walrus 
these are to be observed :—lIst, the great calibre of the axillary trunk previous to giving 
off the subscapular, circumflex, and other muscular branches of the upper humerus; for 
the immense shoulder-masses of flesh giving that wonderful swimming-power to the 
pectoral extremity require sanguineous nourishment accordingly; 2nd, considerable 
diminution of calibre below that point; 3rd, the unity of land-mammalian type as 
regards offshoots from the main trunk, although the flattening and lateral extension of 
the member has much modified the relation of parts; 4th, the tendency to rete mirabile 
in the antibrachium and wrist. 
The descending thoracic and abdominal aorta is very small relatively to the arch; for 
the massive fore limbs and strong muscles of the neck drain much of the blood, whereas © 
* Mém. de l’Acad. de St.-Pétersb. 1835, tom. ii. p. 201. 
