df the Anatomy of the Sea Otter. $8 9 
one small azygos lobe ; the lower lobe sends a process between 
the pericardium and diaphragm. On the left side there are 
two lobes. The lungs were completely empty, so as readily to 
sink in the spirits in which they had been preserved ; the cells 
are very small, and so elastic that they are difficultly expanded# 
and readily collapse. 
The anterior mediastinum 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 upon the other. 
The heart is inclosed in a thin pericardium, is rather short, 
free from fat upon its external surface, and rounded at the apex. 
The ventricles have no communication between them, but the 
foramen ovale between the auricles remained open ; the pas- 
sage 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 pulmonary artery, are the same as in other animals. 
There were no remains of the canalis arteriosus. 
The aorta had nothing unusual in its appearance, but the 
vena cava descendens is very large ; when slit open, its breadth 
is inches. 
The oesophagus is small for the size of the animal. 
The stomach is bent upon itself, the pylorus being on a line> 
with the entrance of the oesophagus, and not at a great dis- 
tance 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 
