REPTILES. 



uiual, the blood of the vena portarum. It enters a large 

 and finglc auricle ; there h alfo a fnigle ventricle, giving 

 origin to a large mufcular artery, fimilar in all points to that 

 of filhes, of the firen, and of tadpoles. It products for the 

 branchix three arteries on each fide, which proceed, as we 

 have already mentioned, along the three firlt arches. The 

 branchial veins are quickly united behind into a fingle trunk, 

 under the back of the head, and this veffel, following the 

 direftion of the fpine, becomes the great artery of tlie body. 

 Thi3 is exaaiy the circulation of the batracian larvne ; and 

 the axolotl, being larger than any of the European ipccies, 

 affords a convenient opportunity of examining this kind of 

 arrangement in the circulating organ. 



Organs of Re/j[>iration.—The branchix of the axolotl, ex- 

 hibiting on a larger fcalc the fame motions as thofe of the 

 falamandrine larvx, the mechanifm can be better underftood ; 

 and the following defcription of the mufcles will, therefore, 

 be received with intereft. 



Each of the cartilages analogous to the hyoideal branches 

 has a very ftrong miifclc, defcending from the bafis of 

 the fkull along their convex fides to their inferior extremi- 

 ties. Thefe mufcles open the branchial arches, by feparat- 

 ing their inferior extremities from the palate. 



The arches are approximated by a mufcle fixed behind 

 to the inferior extremity of the lall, advancing under that 

 of the three others, and giving a (lip to each. Its anta- 

 gonift is a fraall mufcle, fixed, on one fide, te the inferior 

 extremity of the hyoideal branches : and proceeding back- 

 wards as far as under the firil branchial arch, to which it is 

 attached, oppofite to the flip of the preceding. 



The OS hyoides is carried forwards by two genio-hyoidei, 

 and backwards by two pubio-hyoidei : which latter fupply 

 the place, as in the falamanders, both of the fterno-hyoidei 

 and refti abdominis. It is elevated by a mufcle fimilar to 

 the mylo-hyoideus of the fame animals. 



Laftly, the three tufts are themfelves elevated and de- 

 preffed by as many pairs of mufcles, which are attached 

 above and below to the convexities of the branchial arches, 

 and have their other fixed points in the bafes of the tufts. 



The lungs are two large bags, on the internal furface of 

 which the blood-vefl'els form a loofe but very confpicuous 

 net -work. There are no cells. They open into a common, 

 membranous, opaque, and tolerably wide canal, fupplying the 

 place of trachea, but unfurnifhed with cartilaginous rings, 

 and contrafted to form a fmall larynx with two membranous 

 lips. The glottis is imall, formed by two membranous pro- 

 jeftions, behind each of which is a fmall hoUow or ventricle, 

 which may be fuppofed to produce a more powerful voice 

 than that of the firen. 



Organs of Digejlion. — The tongue pofTefles but little power 

 of motion ; it is free in front, but fixed behind to the anterior 

 extremity of the os hyoides. 



The oefophagus is ihort, folded longitudinally, and con- 

 tinuous with the ilomach, which is large and membranous, 

 but confiderably narrowed, and more mufcular towards the 

 pylorus. It was filled, in the two individuals from which 

 this defcription was drawn up, with frefti-water cray-fifli, like 

 the European, which had been fwaljowed without mailica- 

 tion, fo that entire limbs were found even in the reftum. 



The inteilinal canal is tolerably large, particularly behind, 

 and of moderate length. It makes two principal folds, and 

 has neither cxcum nor any internal valve. The liver is 

 reftangular, without any deep notches ; no gall-bladder was 

 obferved. There is a fmall fpleen in the centre of the me- 

 fentery, which is fimplc, as ufual. 



All thefe inteftines are hke thofe of the falamander. 

 Generative Organs.^—The ovaries, fmall, flaccid, and hardly 



containing vifible ova, refemble, in their fituation and fatty 

 appendices, thofe of the falamander. The ovidufts were fo 

 delicate, that they could fcarcely be feen. 



From all the circumilances jull detailed, and from the clofe . 

 refemblance of all its organs to thofe of falamanders, and 

 their larvx, we may conclude, that the Mexican axolotl, or 

 firen pifciformis of Shaw, is the larva of fome large fala- 

 mander. 



Gronvth. — The age of puberty fetms to be the limit of 

 growth in many of this clafs, as in birds, and we may almoft 

 fay, in all mammalia. But others, particularly the croco- 

 diles, turtles, and ferpents, grow conllantly ; of which con- 

 tinual increafe the whales feem to afford an example among 

 mammalia ; at lead, no limits can at prefent be afligned to 

 their ftature. We know little about the length of life of 

 the amphibia. Many, particularly the tortoifes, ferpents, and 

 crocodiles, are prodigioufly long-lived ; coming forth origin- 

 ally from an egg, which is very fmall in comparifon to their 

 future llature, growing very flowly, and reaching an immenfe 

 fi/e. Niebuhr faw at Surat atortoife 12J years old. 



Organs of the Ammal FunBions. 



Organs of Motion. Defcription of the Bones. — We know 

 of nothing peculiar in the organifation of the bony fub- 

 ftance of reptiles. In the larger fpccies, the bones poilefs 

 as much firmnefs as in the mammalia ; but in the fmaller, as 

 the frogs for example, they are more cartilaginous. Cuvier 

 Hates, in general, that the bones of reptiles contain more 

 gelatine than thofe of the mammalia. Caldefi afftrts, that 

 there are no medullary cavities in the tortoife ; according to 

 Cuvier, there are confiderable ones in the crocodiles. Legons 

 d'Anat. Comp. torn. i. p. no. They have never been feen 

 tinged with madder. 



The Head. — A very diminutive cranium, and enormous 

 jaw^make up the head in this clafs. 



As the brain of reptiles and fifhes occupies only a fmall 

 part of the cavity of this cranium, no important confequences 

 can be deduced from its fhape and fize. In the tortoife, 

 this cavity is large, narrow from right to left, elevated 

 anteriorly and depreffed pofteriorly. Its lateral parieteS are 

 almoft vertical, and its bafe is parallel to the palate. The 

 external form of the head, and its apparent magnitude, are 

 occafioned by the acceffory bones, between which and the 

 cranium there is a large fpace occupied by mufcles and 

 glands. The greateft part of the fltuU is occupied by the 

 large lateral hollows, holding the eye, and the powerful 

 mufcles, that move the lower jaw. 



The fmall fize of the cavity of the cranium, with refpeft 

 to the external bulk of the head, is ftill more extraordinary 

 in the crocodile. In an individual four metres long {between 

 thirteen and fourteen feet), that cavity will hardly admit 

 the thumb, and the area of the feftion of the cranium is not 

 one-twentieth part of that of the whole head. ( See a feftion 

 of the fkull of a crocodile in the Annales du Mufeum, tom. x. 

 pi. 4. fig. 5.) The length of the cranium is not one-fifth 

 of the length of the head in the gavials (longiroftres, Cu- 

 vier) ; and it is lefs than one-fourth in the alhgators or 

 caimans (alligatores, Cuv.), and in the true crocodile (cro- 

 codili, Cuv.) The figure of the fedtion is oblong, rather 

 larger anteriorly, and defcending pofteriorly. There is a 

 confiderable depreffion for the pituitary gland. Its breadth 

 is equal to its height ; and the lateral parts of the head, as 

 in the tortoife, cover only the temporal foffx. 



The relative fize of the cranium and jaws undergoes a very 

 remarkable change, in proportion to the gradual develope- 

 ment of the crocodile. The head, when it comes out of the 

 fhell, is thick and rounded, and the forehead prominent ; fee 



Scba, 



