48 COMPARATIVE ANATOMY OP 



their namesakes the Common Dog or Lion. Not that 

 there is no distinction between their respirations, 

 but this difference refers to time only, and not at 

 all to method. Many of the Mammalia breathe 

 twenty times in a minute, and every one knows he 

 cannot long suspend this vital function ; whereas the 

 Seals, instead of breathing twenty times in a mi- 

 nute, will occasionally not breathe once in twenty 

 minutes. We should be happy could we at once 

 account for this difference. The Amphibia often 

 feed under water ; they dive for their prey, they 

 generally swim under the wave, and therefore the 

 attribute is essential to them. It is best, however, at 

 once to avow our ignorance, and to confess that 

 hitherto the fact has not been satisfactorily accounted 

 for. Some peculiarities in their circulation have in- 

 deed been noted, and go some way, perhaps, in the 

 elucidation of the point. Thus, we are told by Baron 

 Cuvier that they have a great reservoir for venous 

 blood in their liver ; and Mr Houston of Dublin has 

 recently succeeded in demonstrating other venous re- 

 servoirs in other neighbouring parts ; and so far 

 this is valuable as a fact, and may assist in the ex- 

 plication of the truth. But it would be a great 

 mistake to suppose that the establishing this anato- 

 mical fact, is the same as explaining how the function 

 of respiration can be suspended in the Amphibia so 

 much longer than in the other Mammalia. These 

 last are not quite destitute of venous reservoirs or 

 sinuses, and, moreover, what is desiderated is not only 

 an apparatus to contain the vitiated, and by many 



