PART IV. 



VISCERA OF ELEPHANT SEAL. 



The heart and some of the .abdominal viscera, and the male and female genitalia, of 

 specimens of Macrorhinus leoninus had been removed and preserved in spirit. 



The heart was from the female killed at Christmas Harbour, and was as big as the 

 heart of a large bullock ; it showed a slight cleft where the two interventricular 

 grooves met at the apex, and each surface was almost equally divided between the two 

 ventricles. 



A broad flattened thymus gland overlapped the ascending aorta and trunk of the 

 pulmonary artery. It measured 150 mm. in transverse and 154 mm. in antero-posterior 

 diameter. It was unequally divided into two lateral lobes, of which the left was about 

 twice the size of the right, and the left in its turn was almost completely subdivided 

 into two portions by intermediate connective tissue. Each lobe was subdivided into 

 numerous lobules, which had no appearance of having undergone fatty degeneration. 

 Two lymphatic glands about the size of walnuts were attached by areolar tissue to the 

 ventral surface of the thymus. 



When the thymus was removed the ascending aorta was seen to emerge from under 

 cover of the pulmonary arterial trunk. Its transverse diameter externally about the 

 middle of its length was 66 mm., but immediately between the origin of the left 

 subclavian and the attachment of the ductus arteriosus the transverse diameter of the 

 arch was only 34 mm. A great contrast was presented between the dilated condition of 

 the ascending and transverse parts of the arch as compared with the descending part, for 

 immediately beyond the ductus arteriosus the transverse diameter of the aorta was only 

 29 mm. The rapid diminution in the calibre of the artery immediately beyond the 

 origins of the great vessels for the head, neck, and anterior limbs would without doubt 

 facilitate the flow of blood into these vessels. 



The ascending aorta close to its origin gave rise to the pair of coronary arteries for 

 the supply of the heart's walls. From the middle of its ventral surface a thymic branch 

 nearly as large as the human radial entered the thymus and was distributed to its 

 substance. From the transverse part of the arch the wide but short innominate artery, 



