REPTILES. 



The mefentery exhibits, in the difTerenl orders of reptiles, 

 lome varieties, which we (hall fliorlly notice. The tirll 

 fold, which is attached to the fmall iiiteiline in the tclhidines, 

 does not come immediately from the vertebral column, and 

 docs not form the mefentery properly fo called, until after 

 it has fixed the arch of tlie colon by means of a mefocolon. 

 The duodenum is confined in the right hypochondrium, and 

 loins, by laminae of the common membrane, which cover it, 

 and are then continued to the abdominal parietes. The me- 

 fentery of ferpents is & narrow fold, not coming immediately 

 from the vertebral column : the blood-veffels form numerous 

 anallomofes between its lamina:, as in warm-blooded ani- 

 mals. 



The faurians have a mefentery tolerably developed. The 

 produftion, which goes to the large inteiline, like that which 

 belongs to the fmall, comes from tlie vertebral column. 

 There is no tranfvcrfe mefocolon. 



Reptiles have no omenta; but ilruclures apparently ana- 

 logous to thefe fatty membranes occur in fome of them. The 

 ferpents have membranous proceli'es, containing much fat, 

 and extending, like the great omentum of the mammalia, 

 under the intellinal canal. Many faurians have alfo two pro- 

 duftions of peritoneum, loaded with fat, advancing from 

 the front edge of the pelvis under the abdominal vifcera ; 

 there are fatty lobes attached to the telticles and ovaries of 

 frogs. The latter are not regarded by Blumenbach in the ' 

 light of omenta. " The yellow appendices," fays he, 

 (duftus adipofi, appendices lutex,) " which are found in the 

 frog, on either fide of the fpine, and fometimes form one 

 raals, fometimes are divided into feveral fmaller portions, 

 were confidered by Malpighi as a kind of omentum. (De 

 omento et adipofis ductibus, oper. t. 2. p. 35, &c.) That 

 this refemblance is very remote, appears from feveral circum- 

 Itances ; and particularly from the conllant and remarkable 

 varialions of fize which occur in thefe parts at the pairing 

 feafon." Comparative Anatomy, tranflated by Lawrence, 



P- "93- 



Thefe bodies, being apparently connefted to the tefticles 



and ovaries, are defcribed with the generative organs by 

 Swammerdam and Roelel. They confiil of a pedicle, at- 

 tached more particularly to the emulgent vein on each fide, 

 and of two, three, to feven or more pieces joined to it, va- 

 rying in fize according to the age and feafon. They are pro- 

 portionally large in the tadpole. They may be feen fmall 

 in female frogs, whicli have not yet laid their ova, although 

 Roefel afierts that they incrcafe in fize with the generative 

 organs. In this fmall Itate, Cuvier obferves, that a veflel, 

 filled with venous blood, and producing no branches, may 

 be feen in the axis of each fringed portion. Thefe veilels 

 all join to form a common trunk in the pedicle ; and this 

 trunk terminates in the emulgent vein. 



The abfence of omentum in this clafs does not accord with 

 its fuppofed ufe to keep the inteftines warm. Is there any 

 proof that the inteftines are warmer with it, than they would 

 be without it ? And is there not as great a ncceflity for 

 preventing the efcape of heat in reptiles, or in birds, ( which 

 alfo have no omentum, ) as in the mammalia ? Cuvier ob- 

 ferves, that many of the hybernating mammalia have two la- 

 teral omental appendices, which, with the principal omentum, 

 are abundantly furniihed with fat in the winter, fo as to form 

 <' an adipous covering for the inteftines, which no doubt 

 contributes powerfully to retain their natural heat, to pre- 

 vent the accefs of cold, and to fupply the place of food." 

 All reptile* are torpid in the winter, yet they have no omenta. 



Urinary Organs. 



The AVi&w.— Thefe are diftingtiiflied from the fame 



glands in mammalia, and refemble thofe of birds and firtiex. 

 in the impodibility of diftinguiftiing in tliem the two fuL- 

 ftsoces (fee Kidney), and in the abfence of iiifundibula and 

 pelvis. Their fituation, form, and relative fize, vary in the 

 different orders. 



In the chelonians and faurians, they lie far back in tlie 

 abdominal cavity. They adhere clofely to the pelvis in 'the 

 lizards properly fo called, under the facruin, and penetrate 

 even under the tail ; they go as far back, but they advance 

 farther in front, in the falamanders. They lie altogether 

 farther forwards, and very near each other, in the other ba- 

 tracians. In thefe three orders both kidnies are fituated at 

 the fame height, and covered by the peritoneum on their in- 

 ferior furfdce only. In the ophidians, the right is placed 

 further forwards than the left ; and tliey are connefted, on 

 each fide of the vertebral column, merely by a prolongation 

 of peritoneum, which lurrounds and fufpcnds them, with- 

 out fixing them to the fpine. There is a manifeft relation 

 between the peculiar arrangement, and the great mobility of 

 the column in thefe animals. 



Their form is fhort and thick in the chelonians, more 

 or lefs elongated and flattened oval in the faurians and batra- 

 cians, and extremely elongated in the ophidians. They 

 confift, in the latter, of numerous feparate lobes, placed in 

 a chain one before the other. They are alfo minutely divided 

 in the chelonians, at leail on their two furfaces ; for all the 

 lobes are united in the centre. They form, on their fur- 

 face, a kind of convolutions refembhng thofe of the brain, ■ 

 and giving the glands a peculiar afpeft. 



Among the faurians, the crocodiles have them much di- 

 vided, at leaft at a certain age. In a fmall crocodile, about 

 a foot in length, Cuvier faw no divifion, while there were 

 many in a larger individual of the fame fpecies. It would 

 be fingular if this fhould turn out to be a conftant difference, 

 as it is exaftly the converfe of that which exifts in man. 

 They are without lobes, or only flightly divided in other 

 genera of the fame order. They have no divifions.in the 

 batracians. 



The origin of the ureters is analogous to that of birds ; 

 and their length varies according to the fituation of the 

 kidnies. 



They end in the urethra in the chelonians, and the urine 

 palTes from that canal into the bladder. 



They are ffiort, large, and thick-fided in the crocodile, 

 and pierce the luperior furface of the cloaca, at a confiderable 

 diftance from each other. 



The principal ramifications of the urinary canals are eafily 

 feen in the ophidians, ending fuccefiively, as they come out 

 of each lobe, in a common trunk, which follows the internal 

 edge of the kidney, and forms the ureter. Arriving near 

 the cloaca, each is dilated into a fmall oval bag, and then 

 terminates feparately. 



In general they terminate in the cloaca or bladder, ac- 

 cording as the latter refervoir exifts or not. 



Urinary Bladder. — Reptiles vary much in refpeft to the 

 exiftence of this part. The chclonian and batracian orders 

 have it : and it is found in the following genera of faurians ; 

 'ji'z. the iguana, tOpinambis, cameleon, dragon, ftellio : 

 while it is wanting in the crocodile, lizard, agame, gecko, 

 other genera of the fame order ; and in the ophidians. 



The bladder is very large, with thin fides and weak muf- 

 cular fibres in the chelonians ; and it has a more or lefs 

 marked divifion at its fundus into two portions. A very 

 fhort urethra opens on the inferior furface of the cloaca : 

 its cavity prefents two prominences on each fide, of which 

 the anterior is pierced by the orifice of the vas deferens, the 

 pofterior by that of the ureter. 



The 



