OECELLA. 391 



In tlie adult animal, tlie aortic arch and great arteries somewhat correspond to 

 tlie condition described and figured by Prof. Turner in the Pilot Whale.^ Erom 

 near the summit of the arch of the aorta two main vessels of considerable 

 caj^acity are given off. These evidently are right and left innominates, sub- 

 clavians of Turner. Half an inch from its origin the so-called left innominate or 

 brachio-cephalic throws forwards and sinistrally a large vessel equivalent to a left 

 subclavian. Prom this at its upper bend there springs from right to left a small 

 branch equivalent to a vertebral (?/.), and which bifurcates a quarter of an inch 

 from its origin. To the left of this vertebral is a slightly larger branch which may 

 correspond to a thyroid axis (it is Turner's transversalis colli), and at about an equal 

 distance to the left is a yet larger branch, the axillary or brachial, while the 

 continuation of the main stem into the chest constitutes the internal mammary 

 artery (m.). The left innominate, about a quarter of an inch above its sub- 

 clavian division, splits into two unequally sized trunks, the inner of which is the 

 larger and may represent the carotid, the outer a trifle less in calibre. 



The right or true innominate artery has a capacity little if at all greater than 

 the left division. There springs half an inch from the aorta and behind it a 

 moderately thick artery which passes upwards and to the right, and supplies the 

 deej) cervical and upper thoracic region of that side {de.). This evidently corre- 

 sponds to the "thoracica posterior dextra" of Turner in Glohicephalus. Derived 

 from the right innominate close above the last, but more to the dextral than the 

 posterior side, and passing beneath or deeper than what shall presently be referred 

 to as the right subclavian, is a fairly- sized vessel, apparently the right axillary artery 

 (ax.^) ; and still higher than it, though almost overlapping it, is a thicker vessel 

 wliich, judging from its position, may be termed the right subclavian (s.*), although 

 possibly objection may be found to this term, as the axillary branch is not continued 

 from it. Prom this main right subclavian trunk, at half an inch distance from its 

 origin, is what I take to be the right thyroid axis {th.^) — an artery springing from 

 its upper border, and which almost immediately thereafter splits into two branches 

 from which subsidiary branclilets are given off. To the right of this thyroidal axis, 

 another smaller artery {tc.)^ which may be equivalent to a transversalis colli, comes 

 off from the right subclavian stem, and it likewise splits into several branches. 

 The continuation of the subclavian trunk meantime courses backwards into the 

 chest forming the large internal mammary artery (m.*) of the right side. This same 

 vessel, as likewise that of the opposite side of the chest, besides supplying blood to 

 the sternal parts, pleurae, etc., proceeds to the peculiar pulmonary glands already 

 described, and each vessel, moreover, seems to join an anastomotic branch derived 

 directly from the abdominal aorta behind the apex of the heart (see fig. 2, m.*). 



In the foetal sj^ecimen of O. brevirostris the arterial distribution in the 

 main corresponds to what has been above described in the adult. There are in this 



» Camb. Journ. Anat. and Physiol, vol. ii. p. 67 ; Knox, Cat. p. 18 ; Eschriclit, Die Nordischen Wallthiere, 

 p. 104; Malm, Anat. Balanoptera Carolina; (Efvers Vet.-Ak Forhandl. 1868, and Barkow, Die Blutegefasse, etc., 

 Breslau. 



