ADDITIONAL NOTE. V. 

 AMPHIBIOUS ANIMALS. 



So stil the Diodons, amphibious tribe, 



With twofold lungs the sea and air imbibe. CANT. I. ]. 331. 



D. D. GARDEN dissected the amphibious creature called diodon by 

 Linneus, and was amazed to find that it possessed both external gills 

 and internal lungs, which he described and prepared and sent to 

 Linneus; who thence put this animal into the order nantes of his class 

 amphibia. He adds also, in his account of polymorpha before the 

 class amphibia, that some of this class breathe by lungs only, and 

 others by both lungs and gills. 



Some amphibious quadrupeds, as the beaver, water rat, and otter, 

 are said to have the foramen ovale of the heart open, which communi- 

 cates from one cavity of it to the other; and that, during their con- 

 tinuance under water, the blood can thus for a time circulate without 

 passing through the lungs; but as it cannot by these means acquire 

 .oxygen either from the air or water, these creatures find it frequently 

 necessary to rise to the surface to respire. As this foramen ovale is 

 always open in the fetus of quadrupeds, till after its birth that it 

 begins to respire, it has been proposed by some to keep young puppies 

 three or four times a day for a minute or two under warm water to pre- 

 vent this communication from one cavity of the heart to the other from 

 growing up; whence it has been thought such dogs might become 

 amphibious. It is also believed that this circumstance has existed in 

 some divers for pearl; whose children are said to have been thus kept 

 under water in their early infancy to enable them afterwards to suc- 

 ceed in their employment. 



But the most frequent distinction of the amphibious animals, that 

 live much in the water, is, that their heart consists but of one cell; 

 and as they are pale creatures with but little blood, and that colder 



