REPTILES. 



mals of lliis clafs, and obtained fimilar refults. DifTerent 

 ff ecies of ferpeiits he found to die in iiydrogcn gas, or when 

 confined under water, but to live in common air, and con- 

 vert its oxygenous portion into carbonic acid. They be- 

 came lethargic from cold, and the heart then heat very 

 {lowly, or not at all, the refpiration was then alfo fiifpcndcd, 

 and little or no effetl was produced in the air. The ikin 

 of thefe animals afted upon the air, as well as tlie lungs 

 (Rapports, &c. torn. i. p. 249.); and when the blood was 

 reddened by expofure to the air, its oxygen alfo difap- 

 peared, and carbonic acid was produced. ( Rapports, &c. 

 torn i. p. 239. 263.) Similar refults were obtained in ex- 

 periments on the refpiration of vipers, tortoifes, lizards, 

 and falamanders. Rapports, &c. tom. i. p. 275. 287. 



?95- 353- 



" The preceding fafts fufficiently (hew, that various ani- 

 mals in all the foregoing clafTes, and in every (lage and 

 foijn of their exiftence, require the prefence of oxygen gas 

 to maintain the funftions of life ; that this gas, by the exer 

 cife of thefe funftions, is converted into carbonic acid ; and 

 that the degree in which this converfion proceeds, depends 

 much on ttie healthy condition of the animal, and the 

 vigour of its circulating fyftem. Since, alfo, in every 

 inilance where the experiments have been made with the 

 requifite accuracy, the bulk, of carbonic acid produced, 

 nearly or exaftly equalled that of the oxygen which dif- 

 appeared, we may conclude, from analogy, tliat fuch is 

 univerfally the extent to which this change in the air takes 

 place in animal refpiration ; and fince, farther, the nitrogen 

 gas of the air appears to futfer no neceHary change in the 

 exercife of this funftion, we may alfo conclude, that as far 

 as regards the air, the fubftitution of an equal bulk of car- 

 bonic acid for the oxygen gas that is loll, comprifes the 

 only eflential change which the atmofphere experiences 

 during the performance of this animal procefs." P. 269 — 

 272. 



l^ital Temperature. — " Since the refpiratory organ?," fays 

 Blumenbach, " may, with great probability, from the nu- 

 merous inveftigations and difcoveries of the moderns, be re- 

 garded as the principal fource of animal temperature, we 

 follow a natural arrangement in palling from the confider- 

 ation of their ftrufture and funftions, to a (liort view of the 

 differences between the natural heat of reptiles and warm- 

 blooded animals. 



" Animals, whofe lungs are mod compaft, receiving the 

 greateft fupply of blood, and furniihed with all the appa- 

 ratus necelfary for fending the whole circulating mafs through 

 the minor circulation, are obliged to keep up the refpiratory 

 procefs uninterruptedly from the time of birth, expelling, 

 inilead of the pure aerial fluid which they infpire, a noxious 

 air, which corrupts the furrounding atmofphere if confined, 

 pofTefs a high natural temperature, about the 98th degree of 

 Fahrenheit's fcale in man, rather higher in foine mammalia, 

 and particularly in birds. In reptiles, on the contrary, 

 poflefling lungs of a rare and loofe texture, with compara- 

 tively llender fupply of blood, refpiration is irregular, inter- 

 rupted, and in fome meafure arbitrary ; they very ilowly 

 vitiate confined air ; and exhibit a temperature exceeding, 

 by a few degrees only, that of the furrounding atmofphere. 

 One or two degrees, I lay, according to the refults of ac- 

 curate obfervation on tortoifes (Walbaum Chelonograph. 

 p. 26.) : for my own experiments on amphibia have not ex- 

 hibited refults fufficiently conftant to allow me to draw any 

 certain inference from them." (Specimen, &c. p. 18.) 

 Braun, indeed, has aflerted, in the Nov. Comment. Acad. 

 Petrop. t. 13. p. 427, that frogs poflefs only the tempe- 

 jrature of the furrounding medium ; but the fafts which 



Vol. XXIX. 



we fhall advance prcfently, completely difprove this af- 

 fertion. 



The power which modern invelUgations have proved 

 w.irm-blooded animals, and more particularly the human 

 fubjett, to poflefs in fo high a degree, of being able to en- 

 dure expofure to heat much above tlie natural temperature of 

 tiie body, without having their own heat increaled ; and, on 

 the contrary, of bearing, with equal facility, the moft in- 

 tenic cold, is not witlilield from the amphibia, as is proved 

 by the fads whicii we have related, in order to (hew the 

 tenacity of hfe in this clafs. It is not, indeed, clear in thefe 

 cafes, as in the experiments, of wliich man and different 

 mammalia have been the fubjefts, that the reptiles, when 

 expolcd to a degree of hear greater or lefs than their own, 

 have maintained tiieir ov 11 temperature at an uniform 

 ilandard ; on the contrary, indeed, it feems that in a great 

 cold their heat is abllracted, and they become frozen ; and 

 it will alfo be feen, from fads to be brought forward pre- 

 fently, that their heat is varioufly changed under dilferent 

 eircumllances. Now we know that the temperature of the 

 mammalia is not railed beyond its natural level by expofure 

 in an atmofpheric medium of 280° Fahr. (fee TiUet in 

 Mem. del'Acad. des Sciences, 1764) ; and that its ftandard 

 is equally undillurbed, when the atmofphere is below the 

 freezing point of mercury. (See Heat, Animal, and 

 Man.) We may therefore fafely aflert that man and the 

 mammalia very far exceed reptiles in the power of refilling 

 either great heat or cold; that is, ot maintaining a Itandard 

 temperature under the aftion of a furruunding atmofphere, 

 coiiliderably exceeding or falling fhort of their own tempe- 

 rature. The following fummary of fads, concerning the 

 temperature of reptiles, is taken from Mr. Ellis's In- 

 quiry. 



" Amphibious animals exhibit a great variety in the 

 (Irudure of the refpiratory organs, and, confequently, in 

 the degrees of animal heat. Frogs and land tortoifes 

 poflefs a temperature about five degrees higher than that of 

 the medium they inhabit, according to Dr. Martine. The 

 fame may be faid of fea tortoifes, toads, vipers, and all the 

 ferpent kind, all of whom have lungs of the fame fabric 

 and the fame cold conftitution of body. (Eifay on Ther- 

 inoracters, p. 142.) Mr. Hunter obferved that the frog 

 and toad were about four or five degrees warmer than the 

 atmofphere when it was at 35*^ or 36° ; and that, fome hours 

 after death, they gradually fell down to the temperature of 

 the furrounding air. (Treatifeon the Blood, p. 298.) The 

 difference of temperature appears to increafe in a warmer 

 atmofphere ; for Mr. Carlifle kept tliree frogs for many 

 days in an equable atmofphere of 54°, and their ftomachs 

 preferved a temperature of 62°. (Philof. Tranfad. 1805, 

 pt. I.) In an atmofphere of 58', Mr. Hunter found the 

 thermometer, introduced into the llomach of a healthy viper, 

 to (land at 68^ ; but, after the animal was put into a pan, 

 and the pan into a cold mixture of 10'', where it remained 

 about ten minutes, the heat was reduced to 37°, and, in 

 twenty minutes more, to 31°, nor did it fink lower; its tail 

 now began to freeze, and the animal was very weak. A 

 frog alfo, whofe temperature was 44°, when put into a cold 

 mixture, foon fell down to 31^; and beyond this point it 

 was not pofTible to leflen the heat without dtltroying the 

 animal. (Obf. on the Animal Economy, p. 104. ) A toad 

 being placed in cold water, jull deep enough not to cover 

 his mouth, the whole was put into a cold mixture between 

 10'^ and 15'-'. The water froze around the toad, and, as it 

 were, doled him in, but he did not die, and therefore was 

 not frozen. Why the animals, mentioned in thefe experi- 

 ments, died before they were frozen, while thofe which are 



s B expofed 



