540 DR. J. MUEIE ON THE ANATOMY OF THE SEA-LION. 



cervical and supiascapiilar branches distributes, as on the right side, a copious supply of 

 blood to the great muscles of the neck, and those in front of and around the shoulder. 



b. Arteries of the Pectoral Limb. 



Axillary artery. — The arbitrary divisions of the subclavian trunk and line of demar- 

 cation between the axillary and brachial artery, which are useful in a surgical point of 

 view in Man, here lose their significance from the absence of a clavicle and the altered 

 condition of the parts. What may be regarded as the axillary artery is little more than 

 one and a half inch long, though of considerable calibre. Several thoracic branches 

 are distributed to the pectoral muscles and to the glands in the axilla. From 

 a quarter to half an inch beyond where these diverge the main artery bifurcates into 

 two equal-sized divisions — respectively the subscapular and brachial arteries. The 

 former relatively large division gives off the circumflex arteries and many muscular 

 branches. 



The subscapular artery pierces the tissues at the i-oot or origin of the subscapularis 

 muscle, and not far from the inner insertion of the episubscapularis muscle. After a 

 short course it subdivides into three groups of branches which, respectively, are spread 

 over the surface of the subscapularis muscle, corresponding to the areas of its trifid, fleshy 

 segments. The dorsalis scapulae, a large branch, proceeds from the subscapular, opposite 

 the neck of the scapula, and goes under the bone between the heads of the dorso-epitro- 

 chlear and triceps, giving branches to these muscles near their origin, after which it joins 

 in front the posterior scapular arteries which supply the parts round the joint. The 

 posterior circumflex pierces the posterior margin of the second division of the triceps — 

 namely, between its small tendinous scapular portion and that arising from the outer 

 neck of the humerus. The anterior circumflex is small, and is distributed to the long 

 portion of the episubscapularis muscle. 



Brachial artery. — Corresponding to the diminished length of the brachial region in 

 Otaria, this artery is short ; moreover it is relatively small ; for the great sanguineous 

 channels supplying the enormous muscular masses of the shoulder are derived higher 

 up than the region in question. The artery is, as usual, accompanied and surrounded 

 by the brachial plexus of nerves and large veins, maintaining a position to the inner 

 side of the median nerve. 



The inferior profunda and the anastomatica magna appear to be derived from one 

 offshoot, which comes from the brachial below its middle, and at half an inch distance 

 divides into two. The upper branch, representing the former, pierces the small triceps 

 muscle. The lower and longer branch, equivalent to the latter, also pierces the same 

 division of the triceps ; but just above or rather deeper than the internal anconeus, it 

 dips deeply beneath the lower (short) triceps and sends a branchlet to the side of the 

 joint behind the internal condyle, the main artery continuing round and above the 

 olecranon to the external anconeus and neighbouring tissues. 



