RESPIRATION. 



opium, in not producing a fubfequent ftate of exhauftion. 

 The defcription of its effe&s in the " Refearches" is very 

 interefting. Mr. Davy infers from his experiments, that 

 this gas is abforbed in large quantities by the venous blood. 

 This blood, when expofed to the gas out of the body, be- 

 comes of a brighter purple, and carbonic acid is formed. 

 We have no doubt, therefore, that carbonic acid is formed 

 when this gas is refpired ; the gas being decompofed, fo that 

 the carbon of the venous blood can unite with its oxygen. 

 We have already fpoken at length againft the notion of any 

 air being abforbed by the blood in brsathing ; and we may 

 refer to Mr. Ellis's Inquiry, chap, iv., for fatisfa&ory argu- 

 ments againft the fuppoled abforption of this gas in parti- 

 cular. 



Hydrogenous gas has been frequently refpired, and it 

 is now pretty generally agreed, that it is altogether paffive 

 when received into the lungs, and that death fucceeds the 

 employment of it in coniequence of the exclufion of oxygen, 

 in the fame manner as by luftocation, or drowning. M. La- 

 voifier diftinftly afcertained this faft, in his experiments re- 

 lated in the memoir of 1789, and it has been fince con- 

 firmed by Mr. Davy. ( Refearches, p. 466.) It mull be 

 remarked, however, that a contrary opinion refpec"ling the 

 effe&s produced by the refpiration of hydrogen has been 

 maintained by forae eminent chemifts, even by Dr. Prieftley 

 himfelf (Obf. on Air, v. i. p. 229.) ; but his experiments 

 were made in the earlier period of the pneumatic chemiftry, 

 when the gafes were frequently employed in an impure ftate, 

 and the experiments of Mr. Davy clearly demonftrate that 

 hydrogenous gas produces different effects upon the fyftem, 

 according to the fubitances from which it is procured. 



The experiments that have been made upon the fubject of 

 azotic gas are few and imperfect ; it has been generally fup- 

 pofed, that it exercifes no noxious effects upon the blood, 

 but, like hydrogen, deftroys life limply by preventing the 

 accefs of oxygen. Dr. Higgins indeed remarks, that an 

 animal dies fooner when immcrled in this gas-, than from the 

 fimple interruption to refpiration (Minutes of a Society, 

 p. 133.) ; but we are not informed upon what data this opi- 

 nion is founded. Mr. Davy likewife experienced the fenfe 

 of fuffocation more fpeedily from the ufe of azote, than 

 from that of hydrogen, but it appears that the gas employed 

 in the experiment contained a quantity of carbonic acid, to 

 which we may, with great probability, afcribe its noxious 

 effects ; and the fame philofopher, when fpeaking in general 

 terms of the action of azote in refpiration, feems to conlider 

 it as merely excluding oxygen. This opinion is adopted by 

 Dr. Thomfon, and was uniformly maintained by M. La- 

 voifier. It would certainly appear reafonable to conclude a 

 priori, that a fubftance which enters fo largely into the com- 

 pofition of the atmofphere, and which confequently com- 

 pofes fo great a proportion of the contents of the lungs, 

 could not exercife any noxious effects upon the animal fyftem. 



The only remaining gafes which can be received into 

 the lungs are the carbonated hydrogen or hydro-carbon, 

 fulphurated hydrogen, and carbonic oxyd. They occafion 

 death immediately, but produce fome change in the blood. 

 If hydro-carbon be infpired in an undiluted ftate, it is fol- 

 lowed by inftant death ; and when employed in fmall quan- 

 tity only, mixed with atmofpheric air or with oxygen, if it 

 be ufed for any length of time, it induces vertigo, dimneis 

 of fight, convulfions, lofs of fenfation, and, in fhort, every 

 fymptom of approaching diffolution. It evidently acts 

 more rapidly and powerfully than thofe gales which merely 

 exclude oxygen from the blood, and mull confequently be 

 considered as cxercifing a pofitively noxious influence upo» 

 the animal economy. For an account of the refpiration of 

 Vol. XXX. 



fulphuretted hydrogen, fee the Journal de Phyfique, vol. lvi. 



P- 35- 



All the remainimg gafes are found to be ftriftly non- 



refpirable, ;'. e. incapable of being admitted into the trachea. 

 It is obvious that this mull be the cafe with the irritating 

 acid or alkaline gafes, and with the nitrous gas, which, during 

 its paffage into the lungs, mull unavoidably be brought into 

 contact with oxygen, and thus produce nitrous acid vapour. 

 The only fubftance, refpecting the refpirability of which 

 there could be any doubt, is the carbonic acid gas, which, 

 though poffeffed of the decided characteriftics of an acid, 

 exhibits them in a much (lighter degree than that in which 

 they generally exift. The impoffibility of taking it into 

 the lungs, even by the moft powerful voluntary efforts, 

 when it compofes a large proportion of the air, was, how- 

 ever, proved by the experiments of M. Pilatre de Rozier, 

 executed with that intrepidity which formed fo remarkable 

 a trait in the character of this philofopher. Boftock'r 

 Efi'ay, p. 149—153. 



He went into a brewer's tub, while full of carbonic acid 

 gas, evolved by fermentation. A gentle heat manifefted it- 

 felf in all parts of his body, and occafioned a fenfible per- 

 fpiration. A (light itching fenfation conftrained him fre- 

 quently to (lint his eyes. When he attempted to breathe, 

 a violent feeling of fuffocation prevented him. He fought 

 for the fteps to get out ; but not finding them readily, the 

 necefiity of breathing increafed, he became giddy, and felt 

 a tingling fenfation in his ears. As foon as his mouth 

 reached the air, he breathed freely, but for fome time he 

 could not dillinguifh objects : his face was purple, his limbs 

 weak, and he underltood with difficulty what was faid to 

 him. But thefe fymptoms foon left him. He repeated the 

 experiment often, and always found, that as long as he con- 

 tinued without breathing, he could fpeak and move about 

 without inconvenience ; but whenever he attempted to 

 breathe, the feeling of fuffocation came on. Journal de 

 Phyfique, vol. xxviii. 



Blumenbach made an experiment on three dogs of nearly 

 the fame fize, to (hew in a comparative view how long three 

 different aerial fluids could fupport life. He prepared a 

 bladder with a pipe attached to it, and holding about 20 

 cubic inches. This, filled with oxygen, was tied in the 

 trachea, and the animal died in 14 minutes. The fecond 

 animal perilhed in fix minutes, when the fame bladder, filled 

 with atmofpheric air, was placed in the fame way in the 

 trachea. The bladder containing the air, at the end of the 

 lad experiment, was put into the trachea of the third animal, 

 which died in four minutes. Inftit. Phyfiolog. 1798, 

 p. 114, note a; or more at length in his Medicinifche 

 Bibliothek, vol. i. p. 174, et fcq. 



VI. EffeRs produced on the Air by the Refpiration of Ani- 

 mals. - The rcfults of obfervation warrant us in allerting 

 that no living being can fubfill long without a fupply of 

 frefh air. That infers die, when their lligmata are covered 

 with oil or honey, has been long known. " Oleo illito in- 

 fe&a omnia exanimantur," fays Pliny. Mr. Derham found 

 that wafps, bees, hornets, and graishoppers, fcemed dead 

 in two minutes, when placed under the exhaufted receiver; 

 but revived in two or three hours, on being rcllored to the 

 air, even although they had remained in vacuo 24 hours. 

 ( l'hyfico-Thcology, p. 8, 7th edit.) Snails furvived feveral 

 hours in the exhaufted receiver, newts two or three days, 

 and leeches five or fix. ( Hutton's Math. Diet, art. Air- 

 pump.) Zoophytes, according to Davy, require air in the 

 water which they inhabit, and ad on it like fifties. (Bed- 

 doi r.'s Contributions, p. 138.) When fome pepper- water 

 had remained in vacuo 24 hours, fome of its animalcules 



1 were 



