RESPIRATION. 125 



hanging, if the lungs be kept distended in the time of hanging, then 

 the left will have the largest quantity. 



As the right side of the heart acts longer than the left, one might 

 suppose that the left side should be the fuller ; but I imagine that its 

 action at this time is with so little force, that no blood is sent to the lungs. 



As most of the blood in the body will always be rather conducted to 

 the larger vessels and of course the heart, and as the right side contains 

 12 where the left contains only 7, does this not support a presumption 

 that the proportion between the [blood of the] body and [of the] lungs is 

 as 12 to 7 ? However, I should think the body [would have] much more. 



The blood being in the larger veins and heart is a proof that the 

 arteries act longer than the veins ; and that the capillary veins act 

 longer than the larger ones, or even than the heart ; and the blood in 

 the left ventricle will be the florid red. 



By letting the blood out of the heart when much distended, it acted. 

 Was this produced from emptying it, or from wounding it ? 



What is the connexion of muscular action with respiration ? For it 

 is well known that violent exercise excites respiration to a great degree. 



The true amphibious animal, if such there be, is such as can breathe 

 both air and water. The turtle, frog, &c, breathe only air ; and are such 

 as can live without breathing for some time, similar to many animals that 

 never go into the water : but they live in and by the air. If these animals 

 are amphibious, all animals are amphibious, although in a less degree ; 

 for all animals can live under water for some time, viz. as long as they 

 can refrain from breathing ; longer than which no animal can live. 



The knowledge of the differences in the circulation in the different 

 classes of animals, has gone no further than [as they exist in] the 

 Mammalia, the human subject, the foetus in such, and what are called 

 the Amphibia : and, of course, every piece of reasoning respecting the 

 circulation, which includes respiration (these being immediately con- 

 nected), has been brought in to explain, upon those differences, the 

 other variations between the two classes of animals. But [the circu- 

 lation] cannot be a cause of such variation ; because other classes of 

 animals shall have the similarities [in regard to circulation] of the one 

 class, while they shall have the varieties of the other 1 : and, in some 

 classes of animals, where the circulation and respiration is the same in 

 the whole class, yet the heart in some shall be like the human, and in 

 others it shall be like the amphibia 2 . 



1 [Birds, for example, have the four-chambered heart and perfect respiration of 

 mammals, but have the oviparous generation and the general plan of structure of 

 Reptiles.] 



2 [Crocodiles, for example, have the four- chambered heart; but with an arrange- 



