14 



THK FUE SEALS. OF THE PRIBILOF ISLANDS. 



al—jl 



The right muscle runs forward about twice the distance of the inner, and divides into 

 an outer and an inner branch. The latter becomes lost upon the ventral wall of the 

 ventricle; while the other bears six chordse tendinae. The third papillary muscle is 

 very short. It projects forward and to the right, into the cavity of the ventricle, from 

 the septum near its ventral border, just back of the right auriculo-veutricular valve. 

 The pulmonary vessels.— The ductus Botalli persists throughout life as a hollow 



vessel, closed at each end by a membrane. It 

 is proportionately larger in a pup than in an 

 old animal, but even in the latter it is well 

 developed. 



There are four pulmonary veins. On the left 

 side one large one comes from the anterior lobe 

 of the corresponding lung and enters the left 

 auricle at its anterior left aspect. From the 

 posterior lobe on the same side three veins, 

 decreasing in size from before backward, con- 

 verge toward the posterior outer aspect of the 

 left auricle and unite near it, forming a single 

 ' trunk less than half an inch long. Ou the 

 right side a very large trunk comes from the 

 most posterior lobe of the right lung and is 

 joined by a smaller vein from the middle lobe. 

 The common trunk thus formed is very short, 

 resembling the one on the left. These two 

 empty very close together into the posterior 

 part of the left auricle. The anterior vein on 

 the right side is formed by the union of numer- 

 ous branches from the anterior and middle 

 lobes of the lung, of which branches the most 

 posterior is the largest, ^nd goes backward 

 and inward dorsad to the right auricle and 

 base of anterior vena cava, to the anterior 

 right aspect of the left auricle. 



The systemic arteries. — The aortic arch gives 

 off two main trunks, the brachiocephalic and 

 left subclavian. The brachiocephalic is very 

 short and gives off close together, first the left 

 common carotid and then the right common 

 carotid. The remaiuder of the trunk continues 

 outward and forward as the right subclavian. 

 Where the latter leaves the thoracic cavity it 

 gives oft' .three principal trunks, the internal 

 mammary, the vertebrfil, and the thyroid amis. 



The internal manimary runs inward and backward along the dorsal side of the 

 costal cartilages just external to the sternum. 



The vertebral artery arises from the subclavian a little internal to the origin of 

 the internal mammary. It runs forward and inward, entering the canal of the verte- 



FiG. 3. — ^Poaterior arterial system. 

 ab. a. Abdominal aorta. 

 ex. il. External iliac. 

 in.il. Internal iliac. 

 al. Allantoic vessels. 

 ep. Epigastric artery. 



