RESPIRATION. 



Sciences for the years 1789 and 1790; but notwithflanding 

 the peculiar advantages under which they were performed, 

 their refults will not be found in all inftances to coincide. 

 M. Seguin was himfelf the fubject of the experiments. The 

 authors begin by pointing out the different effeds which are 

 produced by refpiration, under the different circumflances 

 in which the body is placed ; and they farther remark, that 

 individuals may probably differ in the abfolute quantity of 

 oxygen which they confume in the fame circumflances. 

 Making a due allowance for thefe variations, they conclude, 

 that th* mean confumption of oxygen by a man, during 24 

 hours, is fomewhat more than 22 French cubic feet, or 

 46037.38 Englifh cubic inches ; a quantity of gas which 

 will weigh 15661.66 grains troy. 



Lavoilier was it ill continuing to purfue his experiments 

 ■ in this fubjecl, and had conftruCted a very expenlive appa- 

 ratus, for afcertaining with flill more precifion the amount 

 of the feveral changes produced by refpiration, when he fell 

 a facrifice to the fury of Robefpierre, and received fentence 

 of death. He had already performed a number of experi- 

 ments with his new apparatus, and earneilly requefted a 

 refpite of a few days, in order to prepare them for publica- 

 tion ; but his requett was not granted. M. de la Place, 

 who pronounced his eulogy, has fortunately given us the 

 mod important refults : tkey will be found to differ in fome 

 particulars from the former experiments, though, with re- 

 lpeft to the quantity of oxygen confumed, they nearly coin- 

 cide. It is flated that a man in 24 hours confumes 15592.5 

 grains. 



There are fome experiments on this fubjedt by Mr. Davy, 

 which appear to have been executed with great accuracy. 

 From a number of trials made upon his own refpiration, he 

 found, that 100 cubic inches of atmofpheric air, after hav- 

 ing once pafl'ed through the lungs, had loft between four 

 and five parts of oxygen: hence he calculates, that 31.6 

 cubic inches of oxygen are confumed in a minute ; this will 

 give 45,504 inches in 24 hours, a quantity which will weigh 

 15471.36 grains. This eftimate coincides nearly with that 

 ot M. Lavoilier, though it was obtained by a different pro- 

 cels, and by the ufe of a different apparatus. We may, 

 therefore, conclude, that between 45 and 46,000 cubic 

 inches, or about 15,500 grains = 2 lbs. 8 oz. troy, is the 

 average quantity of oxygen confumed by a man in 24 hours. 

 Davy's Refearches, p. 431 — 434. Eifay on Refpiration, 

 p. 78— 84. 



In the feries of experiments lately performed by Meffrs. 

 Allen and Pepys, an apparatus was employed, in which the 

 volume of the air refpired could be meafured with great ac- 

 curacy, and in which a large quantity (3 or 4000 cubic 

 inches) could be refpired; fo that the fource of error, to 

 which experiments on a fmaller fcale are liable, from the in- 

 fluence of the reiidual air in the lungs, is much diminifhed. 

 They caufed a perfon to infpire, from a gafometer, 3460 

 cubic inches of atmofpheric air, which were afterwards ex- 

 pired into another gafometer ; and to both gafometers gra- 

 duated, fcales were affixed, by which the quantities of air 

 received and expelled could be accurately meafured. The 

 time occupied in the experiment was 11 minutes; about 58 

 refpirations were made ; and the deficiency in the whole 

 volume of air, at the clofe of the experiment, amounted 

 only to 23 cubic inches. One hundred parts of the expil '1 

 air afforded, on analyfis, 8.5 carbonic acid, 12.5 oxygen, 

 and 79 nitrogen gas. (Phil. Tranf. 1808, p. 254.) In 

 an experiment on the refpiration of another fubjeft, the 

 changes produced in the air were the fame, but the quantity 

 confumed was very different. The thermometer (Fahr. ) 

 being at 56 , and the barometer at 30°.3, 3300 cubic 



Vol. XXX. 



inches of atmofpheric air were inlpired, and 3311 expired 

 in 5^ minutes. One hundred parts of the expired air con- 

 fifted of 8.5 carbonic acid, 12.5 oxygen, and 79 azote. 

 When, therefore, twice the quantity of air was pafled 

 through the lungs in a given time, as great a proportion of 

 its oxygen was confumed, and as much carbonic acid 

 formed, as in a fubjeft in whom only half the quantity was 

 breathed. The experiment was repeated feveral times ; and 

 in one inftance, 9890 cubic inches of air were breathed for 

 24! minutes, with the lofs of only 18 cubic inches; and 

 100 parts of the expired air then afforded, on analyfis, 

 8 carbonic acid, 13 oxygen, and 79 nitrogen. (Ibid. 257.) 

 Now the air employed in thefe experiments contained, in 

 100 parts, 21 oxygen and 79 nitrogen; and in the nu- 

 merous analyfes, which were made of this air after its re- 

 fpiration, the portion of oxygen that difappeared was exactly 

 replaced by that of carbonic acid produced ; fo that, in 

 every inftance, thefe two gafes formed together -,=„',, ths of 

 the refpired air, the remaining 79 parts being pure nitrogen 

 gas. It is, therefore, concluded, that the quantity of car- 

 bonic acid gas emitted is exattly equal, bulk for bulk, to 

 the oxygen confumed. Ibid. p. 279. 



In fubfequent experiments on the refpiration of a guinea 

 pig, thefe chemifts found, that when 310 cubic inches of 

 atmofpheric air were breathed tor 25 minutes by this animal, 

 its volume experienced no variation whatever ; and the por- 

 tion ot its oxygen, which difappeared, was replaced by an 

 equal bulk of carbonic acid. (Phil. Tranf. 1809, p. 414.) 

 Three experiments were made on the refpiration of the 

 guinea pig, in two of which the time occupied was 25 mi- 

 nutes, and in the third one hour. The animal was confined 

 in a certain volume of air, which was changed fucceffively, 

 fo that the fame air may have been breathed more than 

 once ; while in the experiments of thefe gentlemen on hu- 

 man refpiration, juft detailed, the air was only once 

 breathed. In all the three experiments with the guinea pig, 

 too parts of the air breathed contained the fame confti- 

 tuent elements, -viz. 5 carbonic acid, 16 oxygen, 79 azote. 

 (Phil. Tranf. 1809, p. 413, et feq.) Wherefore, they 

 juftly conclude, that when atmofpheric air alone is refpired, 

 even by an animal fubfiiting wholly on vegetables, no other 

 change takes place in it than the fubilitution of a certain 

 portion of carbonic acid gas for an equal volume of oxygen. 

 Ibid. p. 427. 



In refpiration as nearly natural as pofTiblc, thefe gentle- 

 men eftimate the quantity of ox\;> ;n consumed on an 

 average at 26.6 cubic inches, at the temperature of 50 , 

 and barometrical preflure of 30 .4. 



The changes occurring in refpiration are influenced by 

 various caufes, which modify the actions of the capillary 

 veffels. Crawford eftablilhed by experiment, that lefs oxy- 

 gen is confumed at a high than at a low temperature (Ex- 

 periments on Animal Heat, p. 307.) ; and this was con- 

 firmed in the experiments of Lavoilier and Seguin (Mem 

 de l'Acad. des Sciences, 1789, p. 575.) ; a man confuming, 

 at the temperature of 54', 1344 cubic inches of oxygen in 

 an hour, while, in an atmofphere at the temperature 01 79°, 

 he confumed only 12 10 cubic inches. Crawford obferved 

 alfo, that in an animal placed in a warm medium, the venous 

 blood approached to the arterial in colour. Hence it ap- 

 pears, that the high temperature counterac 1 1 thofe chemical 

 changes which the blood undergoes in the extreme vct'els ; 

 and that the diminution in the conlumption ot oxygen b> 

 refpiration is owing to this caufe, and not, as has been fup- 

 pofed, to the rarity of the air at the high temperature. It 

 the confumption of oxygen were diminifhed from the lattei 

 caufe, the blood ought to be even more completely venou? 



G thai 



