333 ON THE ALLIGATOR 



into the left aorta. On the other side, the pulmonary veins 

 bring the blood from the lungs into the left auricle, which 

 discharges it into the ventricle of the same side ; from thence 

 it is propelled into the right aorta, the right subclavian, and 

 the carotid artery. It appears, that the circulation goes on 

 in this manner whilst the animal is allowed to breathe ; but 

 when it is confined under water, when the lungs have ceased 

 in part to perform tlieir office, the right ventricle must send a 

 greater quantity of blood into the left aorta, which becomes 

 filled with an increase of the fluid ; the weight and pressure 

 must act on the valve, which, as I have already observed, 

 allows but a very small quantity (if any) of the blood com- 

 ing from the left ventricle to penetrate into the left aorta. 



M. Cuvier describes the ventricle as being divided hUo 

 three cells, communicatiTig xvith each other by many orifices. 

 1 have proved, if my observafions are correct, that there are 

 two ventricles, very distinct, and having no manner of com- 

 munication from one to the other through their partition : 

 only nature has placed a large arterial tube (the left or 

 splanchnic aorta,) which has a communication with the 

 right or systemic aorta, and which being capable of great 

 distention, when filled with the fluid, empties part of its con- 

 tents into the right aorta. 



This structure which M. Cuvier thinks analogous to that 

 in the cheloniens, differs essentially from it. In turtles, a 

 mixture of arterial and venous blood takes place in the ven- 

 tricle : whilst in the alligator, when the left aorta becomes 

 much distended with blood, which must be the case when 

 the animal is under water, this artery may supply the left 

 ventricle with part of its contents, but the two semilunar 

 valves placed at the orifice of the right ventricle into this 

 tul)e prevent the introducfion of any part of the fluid into 

 it from the arterial canal, so that the lungs never receive 

 blood which has not passed through the system. Moieover, 

 when the animal is exposed to tlie atmo'^phere, when the 

 lungs receiving the regenerating element, allow the venous 

 blood to flow towards these organs, both ventricles must re- 



