REPTILES. 



ported liiii), about half way up tlie jar, was placed a iinall 

 oip, containing one cubic inch of the water of potada ; and 

 tlie jar beinjr then filled with atmofpheric air, was inverted 

 into a dilh ot' mercury, and keptiteady by a weight preiling 

 upon it. In the room in which the animal was placed, the 

 barometer ftood at 29.2 inches, and the thermometer at 61°. 

 At the end of twenty-nine hours, the animal was refting 

 quietly on the hoop, with no appearance of diftrels, and 

 the mercury in the jar, when that in the difh was brought 

 to a level with it, had rifen fix-tenths of an inch. In 

 twenty-four hours more, the frog was dill alive : his refpi- 

 ration feemed now to labour, and he rofe often to the top 

 of the jar, as if defirous of efcaping, or of obtaining frefh 

 air : the mercury had now rifen to 1.15 of an inch. From 

 this time, the difficulty of breathing continued to increafe, 

 and, at the clofe of the fifty-ninth hour,- from the com- 

 mencement of the experiment, after having lain quiet for a 

 confiderable time, he gave a convuUive ftruggle, and moved 

 no more. The mercury in the difli was now brought to a 

 level with that in the jar, and its height was 1.2 of an inch. 

 The barometer, at this period, was 29.8, and the thermo- 

 meter 65°. 



" In order to examine the refidual air, we plunged the dilh 

 under water, which rifing into the jar, difplaced the mercur)', 

 and the cup, with its folution, was then withdrawn under 

 water. Tlie refidual air fuffered no diminution by being 

 fhaken with lime-water, nor by contaft with phofphorus, 

 but it lolt rather more than xi « by agitation with the liquid 

 fulphuret of potafTa. The jar originally held forty cubic 

 inches, but the animal, with the hoop, cup, and folution, 

 occupied a (liare equal to four, fo that the adual bulk ot air 

 employed was 36 cubic inches. Having placed the jar on 

 its bottom, water, to the quantity of 27 cubic inches, was 

 poured in till it reached the point to which the mercury, 

 during the experiment, had rifen ; and this, therefore, indi- 

 cated the volume of refidual air : it then required nine cubic 

 inches more of water to fill the jar completely, which, confe- 

 quently, was the bulk of air that had difappeared. Hence, 



therefc 



have 



27 X 29.8 



= 22819 and 27.554 

 rafted volume of air 



29.2 



= 27-5547. but 



4x27.554 



at 



4-15 



483 

 .22819 = 27.32651, the cor- 

 the clofe of the experiment. 



8.62349 

 36 



fo that the diminution of bulk which the air fuffered 



But farther, 36— 27.32651 = 8.67349, 



and , — =z 



in this experiment is rather greater than 



4-54 



the propor- 



tion of oxygen gas which the atmofphere contains. In a 

 fecond experiment, another frog lived in the fame volume of 

 air about 60 hours, and the diminution which it fuffered, 



after making the necelfary reduftions, amounted to — — — 

 ° ' 4.868 



of the whole. Where the carbonic acid, formed by the re- 

 fpiration of another frog, was fuffered to remain, the jar, 

 after the death of the animal, adhered firmly to the faucer 

 in which it was inverted, and, when cautioufiy elevated, the 

 furrounding mercury rufhed in ; and occupied only about 

 one-tenth of the fpace which it filled in the above-mentioned 

 cafes : the inferences deducible from thefe fafts, inftruA us, 

 that the diminution which atmofpheric air iuffers by the 

 refpiration of thefe animals, bears a near proportion to the 

 oxygen gas which it contains, when all the carbonic acid is 

 removed : and as a fmall lofs of bulk likewife takes place 



when tliis .acid is allowed to remain, we tnuft afcribe a part 

 of the obferved diminution to tlie necell'ary lofs which al- 

 ways accompanies the converfion of oxygen gau into car- 

 bonic acid. 



" It follows from the preceding feries of experiments, that 

 the oxygenous portion of the air is changed by the refpira- 

 tion of amphibious animals in the lame manner as by that of 

 the other claflcs, carbonic acid, in proportion thereto, beino-, 

 in all cafes, produced ; and that when the whole, or nearly 

 the whole, of that gas is fo changed, the animal no longer 

 furvives. But, if the animal die when all the oxygen gas it, 

 changed, and all llie air that has difappeared when the car. 

 bonic acid is removed, be oxygen gas, then the bulk of air 

 that remains, and is unchanged, mult confift wholly of ni- 

 trogen gas ; and as this nitrogen gas, joined with the oxy- 

 gen gas that has difappeared, makes up the v/ho!e bulk of 

 air originally employed, it follows a!fo, that, while the 

 oxygen gas of the air has diminiflied and fullered change, 

 the nitrogenous portion has continued undiminifhed and 

 unaltered. 



" During all thefe changes operated on tlie air contained 

 in water, by the refpiratory functions of aquatic animals, the 

 water itfelf feems to fuffer little or no alteration. Mr. Car- 

 lifle took I'eparate glafles, each contaifiiiig one pound of 

 diftilled water, which was previoufly boiled to expel all its 

 air, and then inverting them over mercury, he put into them 

 one gold fifh, one trog, two leeches, and one frefh-water 

 mufcle. The animals were confined feveral days in thefe 

 fituations, and expofed to the fun during January, in tem- 

 perature 43^^ and 48" Fahrenheit ; but 110 air-bubbles were 

 produced in the vellels, nor was there any fenfible dimi- 

 nution of the water. The frog died on the third day, the 

 fifli on the fifth, the leeches on the eighth, and the mufcle 

 on the thirteenth day. This experiment was made to afcer- 

 tain the changes produced in water by the refpiration of 

 aquatic animals ; but the water had not undergone any 

 chemical alteration. See Croonian Lecture in the Philol. 

 Tranf. 1805." Inquiry, p. 83 — 88. 



Mr. Ellis adduces fome additional evidence in his Further 

 Inquiry. " The experiments already detailed in the former 

 work clearly prove, that frogs and toads which belong to this 

 clafs, entirely convert, by refpiration, the oxygen gas of the 

 air into nearly an equal bulk of carbonic acid, without pro- 

 ducing any change in its nitrogenous portion. Dr. Carra- 

 dori alfo difcovered, that thefe animals lived much longer 

 when they were immerfed in water tflat had a free commu- 

 nication with the atmofphere, than when the air was ex- 

 cluded. (Phil. Mag. vol. 16. p. 245). According to 

 Spallanzani, frogs die fooner in boiled, than in common 

 water. In their refpiration, they confume oxygen, and 

 form carbonic acid. Thofe which have been recently fed, 

 confume more of this gas than thofe which have fuffered a 

 long abftinence. Under great cold they become lethargic, 

 but their heart flill continues to beat, and they ftill, in a 

 fmallcr degree, continue to change the air ; but the con- 

 fumption of oxygen increafes with the increafe of tempe- 

 rature. Thefe animals alfo change the air by their (Idn, 

 as well as by their lungs ; and att upon it after death, and 

 under putrefaction. (Rapports, &c. torn. i. p. 468.) The 

 ova of frogs were likewife found to require air to carry on 

 their evolution. Small tadpoles, while yet attached to the 

 egg, were confined in vefTels half filled with water, while 

 the other half contained air, or oxygen or nitrogen gas. 

 Thofe in the two former veflels were perfeftly developed, 

 and became large enough to fwim about ; but thofe confined 

 with nitrogen perifhed. Rapports, &c. tom. i. p. 466. 

 " SpaUanzani extended his experiments to many other ani- 



6 mals 



