REPTILES. 299 



M. CuviER speaks only of six arteries, three on each side, 

 going to the gills ; but as, by the aid of injections, we have 

 found, say the authors, that, in the larvae above named, 

 there are eight vessels, and that the artery which runs along 

 the interior arch of each side, and which M. Cuvieii has 

 not seen, is that which in process of time becomes the pul- 

 monary artery, so, guided by analogy, we hold it for cer- 

 tain, that, as the siren is furnished with eight branchial 

 arches entirely similar to those of the other larvae, there are 

 also eight arteries, four on each side, corresponding to them. 

 And, proceeding on this opinion, we may remark a striking 

 difference in the circulating system of the siren and proteus, 

 since the artery, properly called Pulmonary, which is found 

 in the siren and larvag above mentioned, does not exist in 

 the proteus. Doubtless in the proteus, the air-bladder, like 

 every other part of the body, is duly supplied with blood ; 

 but the blood sent to it is furnished by an artery coming 

 oft", on each side, from one of the aortic trunks, and which 

 artery, descending along the canal of the bladder, gives to 

 it a branch, and is then continued to the ovary or testicle 

 in each sex respectively. 



" Besides these differences in the arterial, there are others 

 in the venous system ; for the vessel which returns the 

 blood from the air-bladder of the proteus, does not empty 

 itself directly into the cava or the auricle, as is observed in 

 other reptiles ; but into the vein which carries back the 

 blood from the organs of generation, which itself enters the 

 cava above the middle of the kidney ; hence in the proteus, 

 not only the true pulmonary artery, but the vein also, is 

 wanting. This anatomical fact, ascertained by repeated in- 

 jections, might alone be sufficient to demonstrate, that the 

 two air-bladders with which the proteus is furnished are 

 not true lungs : but as some, perhaps, may not yield to the 



