109 
and Structure of the Proteus Anguinus . 
open into the mouth. This circumstance prompted us to exa- 
mine the condition of the bones of the face in these larvae, and 
we have thereby satisfied ourselves that the larva of the sala- 
mander is unable to breathe by lungs, until the maxillary bones, 
the zygomatic arched, and the palatine bones are sufficiently 
developed to form the canal of the nostrils, in such a manner 
that its posterior extremity may open into the mouth. Before 
this canal is so formed, these larvae are unable to respire atmo- 
spheric air, and, if taken out of the water, they then soon die ; 
and, therefore, guided by analogy, we incline to the belief, that, 
to the siren, whose nostrils 44 ne penetrent point dans la bouche,’’’’ 
the same things ought to happen. Moreover, as its lungs are 
similar in all respects to those of the salamander, and are fur- 
nished with a true glottis, we are farther of opinion, that the 
siren is the larva of some reptile, the genus of which is as yet 
unknown, and which will differ from its larva in not possessing 
gills, and in having a trunk somewhat longer. 
To return to the proteus. — We consider that it is not an am- 
phibious animal, having a double circulation, as some have 
maintained, but a perfect reptile , different entirely from all 
others. It is a reptile, in respect to its having a single circula- 
tion, and a fish, in regard to its mode of respiration, — in other 
words, it is a reptile which respires air mixed with water, while 
others respire atmospheric air : so that, were it allowable to re- 
vive the old idea of a chain of beings, the proteus might be 
regarded as the link which would connect reptiles with fishes. 
From the facts and circumstances above stated, it appears, 
that the proteus is an animal, which, like fishes, is capable of 
respiring only in water. Its branchial circulation, however, 
is only a fraction of the greater circulation, whence it follows, 
that, in respiration, it consumes less oxygen than fishes do ; 
and, consequently, a smaller quantity of blood in a given time 
is changed in the gills of the proteus, than, in like circumstances, 
is changed in the gills of fishes. From this circumstance, as 
appears to us, continue the authors, arise the inertness, the 
slow growth, the capacity of enduring fasting, the indisposition 
in the blood to coagulate, and, lastly, the power of living in a 
stagnant water, where a fish of equal size would die. With re- 
gard to the faculty of generating heat, the authors are unable 
