THE ANATOMY OF THE WEDDELL SEAL. 73 



ring the inferior vena cava passed. From the ventral face of this tendinous ring strong 

 muscular bands extended to the deep face of the broad ensiform cartilage. 



From each side of the dorsal segment of the fibrous ring surrounding the inferior 

 vena cava there extended a narrow tendinous septum in the dorso-lateral direction. 

 Neither of these septa reached the ribs, although the one on the right side was more 

 strongly marked than that on the left side. Into the dorsal faces of these septa there 

 were inserted muscular fibres derived from the lateral aspects of their respective crura, 

 as well as a small, feeble muscular slip from the ventral surface of the second last rib 

 (the 14th) near its head. 



From the ventral aspects of the tendinous septa under consideration, a sheet of 

 muscular fibres passed outwards to be attached by slips or digitations into the ribs close 

 to their junction with cartilages from the 8th to the 13th inclusive. The digitation be- 

 longing to the 13th rib was attached just in front of the angle of the rib. This ventro- 

 lateral part of the diaphragm was very thin. Areolar tissue occupied the intervals 

 between digitations attached to the 13th and 14th ribs, and also between the 14th rib 

 and the lateral margin of the crus. The association of the diaphragm with the 15th rib 

 was so feeble as to be doubtful. Probably these weak places may be regarded as corre- 

 sponding to arcuate ligaments, although in the human sense these structures were 

 undefined. At any rate, these arched ligaments had no other representation, neither 

 could the slight intermingling of crural fibres on the ventral aspect of the aorta be 

 regarded as other than a very feeble median arched ligament. Altogether the dorso- 

 lateral development of the diaphragm was extremely feeble. Those muscular fibres 

 attached to the 8th rib were in close contact with the mesial part of the diaphragm 

 between the sternum and the fibrous ring enclosing the inferior vena cava. 



From what has been described it will be evident that there was no central tendon of 

 the trefoil pattern, but in its place a vena caval ring, from which there extended two 

 dorsal-lateral septa, of which the right was the stronger marked. The shortness of the 

 left septum permitted a greater mingling of the fibres belonging to the left crus with 

 those forming the rest of the left half of the diaphragm. 



The general arrangements within the chest cavity do not call for special discussion. 

 The two pleural sacs and the mediastinal interval followed the customary disposition. 

 It may, however, be noted that the mediastinal layers of pleural membrane were in close 

 apposition from the second segment of the sternum backwards to the hinder end of the 

 sternum, and that consequently the ventral or anterior section of the mediastinum was 

 a mere chink, in its sternal relations. 



The lungs were extremely dark in colour, brown almost to black. They were quite 

 soft, but yielded no feeling of crepitation on pressure, so that they suggested a complete 

 absence of air. 



When they were removed each was placed in water, and they sank as if solid. A 

 small portion cut from the lung also sank in water, so that this tissue had entirely lost 

 its buoyancy. It is not quite easy to account for such a complete absence of air from 



(ROT. soc. KDIN. TRAMS., VOL. ZLVIII., 323.) 



