23 



through the lungs, is still more completely mingled with that which has not been 

 submitted to this action, and which is just returned from the body to the heart. 



The mode of life of the reptilia, most of whom are amphibious, renders this 

 peculiarity in the structure of the heart necessary. The corporeal, or greater, 

 circulation is, in these animals, in some measure independent of the lesser or pul- 

 monary one ; for, in warm-blooded animals, no blood can pass into the left 

 ventricle, and thence to the body, which has not previously passed through the 

 lungs ; the aorta, a vessel which propels the blood to the body, arising, in all 

 warm-blooded animals, from the left ventricle, and not from the right as in the 

 reptilia. The blood cannot pass through the lungs except the animal breathes ; 

 consequently, no circulation could go on as long as the animal was under water : 

 but from the peculiarity of the structure of the heart, we find that the blood 

 passes directly from the right auricle to the right ventricle, whence the aorta 

 arises, and the blood is sent straight on to the body again, without passing through 

 the lungs, as in warm-blooded animals. This circulation, however, cannot go on 

 ad infinitum, with this decarbonized blood, and the reptile is obliged to seek the 

 atmosphere at certain intervals, to take in supplies of air. I do not agree with 

 Blumenbach entirely, when he supposes that the general or corporeal circulation 

 alone goes on when the reptile is under water ; since the peculiarity of the lungs 

 of the amphibia enables them to take in a supply of air which will last for a con- 

 siderable time, and hence some degree, if not a perfect one, of arterialization of 

 blood goes on when the animal is under water, as well as when he breathes atmos- 

 pheric air. We may suppose, however, that a less quantity of blood passes 

 through the lungs during the time the animal is under water, than when breathing 

 air, and consequently the blood must be more imperfectly decarbonised at this 

 time than at others, though under all circumstances the blood of the reptilia is of 

 a lower temperature and of less stimulating character than in the animals of the 

 classes of the aves and mammalia. 



L. P. 



ANIMAL PROGNOSTICS. 



Every observer of Nature must have often remarked with what certainty 

 many animals give signs of a change in the weather. Those signs are, with us, 

 most conspicuous in the summer ; and it is of rain, and not of fair weather, that 

 they are given. Swifts and Swallows, though not one has been seen on the wing 

 during weeks of drought, fly with ceaseless rapidity; and the former shrink 

 from the top of the sky whenever the clouds above them are elaborating rain, and 

 especially if that rain is accompanied with thunder. It is true that these birds do 



