550 
OBSERVATIONS ON THE 
ever, it may be said, that, in the Rodentia, the passage of 
the bile and pancreatic fluid into the intestines is much 
apart. I consider it unnecessary to dwell on the minute 
anatomy of the intestinal canal or generative organs, as it 
would be difficult to add any thing to the descriptions of 
M. CuviER, contained in the celebrated works of that dis- 
tinguished anatomist. I could not perceive the least dif- 
ference in the lungs from those of the class Rodentia. 
The peculiarity in the structure of the venous system I 
have just described, is, no doubt, connected with the habits 
of the beaver as an aquatic animal. That it is exposed 
occasionally to long submersion, we may readily imagine, 
as well in escaping from its enemies, as passing under the 
ice in winter. In some animals whose habits are similar, 
we are assured that a similar venous sinus exists : it has 
been remarked in the seal, and in diving birds, as the duck ; 
but I have observed that, in birds of this kind, the whole 
venous system is remarkable for the large caliber of the ves- 
sels ; for their number, and for the frequent and extensive 
plexuses they form in almost every part of the body. The 
golden-eyed duck presents this appearance most remark- 
ably. 
It is extremely probable that this theory, drawn from 
anatomical facts, and supported by the authority of Blu- 
MENBACH, would have been universally adopted long ago, 
but for the limited views of the strictly human anatomist : 
these led to some curious, but uninstructive experiments in 
France, which contributed to throw the subject into still 
greater confusion. The foetal circulation of the mammalia 
was transferred by a false analogy to the full-grown Cetacea, 
and to other aquatic animals : it was supposed that these 
animals were amphibious, by reason of the peculiar distri- 
bution of vessels, and of structure, enabling the blood to 
pass from the right to the left side of the heart, witliout 
