36 PHILOSOPHICAL TRANSACTIONS. [ANNO 17Q6. 



elastic that they are difficultly expanded, and readily collapse. The anterior medi- 

 astinum is of considerable breadth, but free from fat, consisting of nothing besides 

 the duplicature of the pleura. In the foetus there is a very large thymus gland, 

 convex on its external surface, and concave on the other. The heart is inclosed in 

 a thin pericardium, is rather short, free from fat on its external surface, and rounded 

 at the apex. The ventricles have no communication between them, but the fora- 

 men ovale between the auricles remained open ; the passage was however so oblique, 

 that it must have acted as a valve ; it admitted a crow quill. In the foetus it was 

 less oblique. The structure of the heart, and the valves of the aorta and pulmo- 

 nary artery, are the same as in other animals. There were no remains of the ca- 

 nalis arteriosus. The aorta had nothing unusual in its appearance, but the vena 

 cava descendens is very large ; when slit open, its breadth is 54- inches. The oeso- 

 phagus is small for the size of the animal. 



The stomach is bent on itself, the pylorus being on a line with the entrance of 

 the oesophagus, and not at a great distance from it. The cardia does not project 

 much into the left hypochondre ; and that half of the stomach next the pylorus is 

 much smaller than the other. The coats are thin. The internal surface is free 

 from rugae ; the posterior portion is smooth, without any appearance of glandular 

 structure ; the anterior portion is more vascular and villous. At the pylorus there 

 is an oval part of the internal surface of a dark colour, and rougher or more villous 

 than the rest of the stomach, with a determined edge ; the small end of the oval 

 extends about 4- an inch beyond the pylorus into the duodenum ; the larger end 

 goes some way into the stomach, and extends chiefly over the posterior surface, also 

 a little way beyond the great arch anteriorly, covering about 4. the breadth of this 

 part of the stomach ; it is nearly as long again as it is broad. This part is pro 

 bably glandular ; it was only seen in the young subject, which from the smallness 

 of its size was more perfectly preserved, and its internal parts better fitted for ana- 

 tomical examination. At the pylorus there is the usual thickened valvular appear- 

 ance. The stomach was entirely empty, and in a very flaccid state. 



The duodenum makes a considerable bend downwards on the right side before it 

 crosses the spine, to become a loose intestine ; there is no coecum or difference of 

 size in the intestines, they are all strung upon the mesentery till within ] 5 inches of 

 the anus ; this part of the gut crosses the spine above the root of the mesentery, 

 and passes down to the anus. The intestines have no valvulae conniventes ; they 

 were 52 feet long, which is 12 times the length of the animal, In a common otter, 

 the intestines are only 34- times the length of the animal. In a common otter 2 

 bags are found at the anus, but there are none in the sea otter. The mesentery is 

 7 inches broad, and its lower part, which may be called meso rectum, is only 5 

 inches in breadth. The mesentery is thin, and has a great many blood-vessels 

 which are accompanied with fat. There are no lymphatic glands on the general 

 membrane, but a cluster of very large ones close to the root of the mesentery. 

 The lacteals appear a little larger than in the human subject, but the circumstance 



