RESPIRATION. 



duce condenfation of the air they contain. But independent 

 of this, it is well known, as Mr. Ellis remarks, that a 

 ftrong attraction or adhefion is exerted between air and the 

 ftirfaces of all bodies ; the more, therefore, the furface is 

 nicreafed, the greater muft be the effect from this attractive 

 force. Hence, under the extenfive furface ot the cells of 

 the lungs, it muft operate with great effect, and reduce 

 confiderably the volume of the air. The ibiorption of 

 aerial fluids by charcoal, Mr. Ellis adduces as illuftrating 

 this operation of adhefion ; and in the lungs it is fufhciently 

 probable, that it may be aided by the affinity exerted by 

 the humid furface to the aerial matter. 



All the phenomena accord much better with this view 

 than with the conclulion that nitrogen is evolved from the 

 blood. Thus the " production of nitrogen is always 

 greateft in the firft expiration, and its quantity progreffively 

 diminishes, until towards the clofe of the experiment, it is 

 reduced almoft to nothing, circumftances which feem plainly 

 to £hew that nitrogen is no longer obtained when all the 

 refidual air in the lungs is removed. If this nitrogen were 



O O 



furniihed by the blood independent of the refidual air, no 

 reafon occurs why it fhould thus diminifh, and ceafe to 

 appear, as this air is abftracted ; for the function of refpira- 

 tion goes on, and the blood, as far as depends on itielf, can- 

 not be confideredleis tit to fupply nitrogen. The fact, alfo, 

 that no fuch excefs of nitrogen is furniihed in natural refpir- 

 ation, militates againft the notion of its proceeding from 

 the blood. No excefs of nitrogen, too, is ever afTorded in 

 other cafes, unlefs its place be iupplied by an equal or fupe- 

 rior bulk of fome other gas. And this affords evidence, 

 that in this fuppofed evolution of nitrogen from the blood, 

 nothing more than a mechanical fubftitution of one gas for 

 another takes place." (Farther Inquiries, &c. p. 306.) 

 Murray's Syftem of Chemiitry, 3d edit. v. 4. p. 498, et 

 feq. 



Adopting, as we do entirely, the views of Mrt Ellis on 

 the fubject of refpiration (to whofe clear, logical, and very 

 fatisfactory works we refer our readers for more ample in- 

 formation), we conclude our review of the changes, which 

 the atmofphere undergoes in reipiration, in the words of his 

 " Further Inquiry," $621. 



" From the foregoing feries of facts, concerning the re- 

 fpiration of the higher claffes of animals, we feel ourfelves 

 entitled to repeat with increafed confidence, that ' the 

 whole of the oxygen gas which difappears in refpiration is 

 employed to form the carbonic acid produced in that pro- 

 cefs-' And that ' the nitrogen gas of the air neither 

 fuffers any change itfelf, nor produces any direct operation 

 on the animal fyttem.' Or, in the words of Meffrs. Allen 

 and Pepys, ' When atmoipheric air alone is refpired, no 

 other change takes place in it, than the fubftitution of a 

 certain portion of carbonic acid gas for an equal volume 

 of oxygen.' (Phil. Tranf. 1809^.427.) Confequentlv 

 in man, as well as in the lower animals, the converfion of 

 oxygen gas into carbonic acid conftitutes the onlv eiTential 

 change, which the air of our atmofphere experiences in the 

 lungs during its refpiration." 



Aqueous Vapour contained in the expired Air. — That the 

 air expelled from the lungs contains a certain quantity of 

 watery vapour, is rendered very obvious by its condenfa- 

 tion, when we breathe cold air. It is not very eafy to 

 afcertain its quantity. 



Dr. Hales performed many experiments for this purpofe : 

 he contrived to pafs the air which he expired through a 

 flafk filled with woodaihes, which, in confequence of the pot- 

 afh contained in them, have the property of llronrlv at- 

 '.raiting the moifture. By obferving the incrcafe of weight 



which the acid had acquired in a given time, he eftitnates 

 that the water em.tted from the lungs in 24 hours, will 

 amount to 9792 grains, above 20 ounces. ( Statical Effays, 

 v. 2. p. 322—4.) The nature of his procefs, however, 

 did not admit of much accuracy. Dr. Merges attempted 

 to folve this problem, by actually collecting in an allantoic! 

 htted to the mouth, the water emitted from the lungs in a 

 given time ; his eitimatc is much lefs than that of Hales ; 

 he iuppofed that the quantity of water exhaled in 24 hours 

 would amount to no more than 6 ounces, or 28S0 drains. 

 (Dillertation on Refpiration, p. 54.) Mr. Abernethv, by 

 breathing into a glafs veffel of a peculiar conftruction col- 

 lected m an hour 1S0 grains of water, containing, as he 

 iuppoied, a quantity of mucous matter. According to his 

 eltimate the quantity emitted in 24 hours, would amount 

 to exactly 9 ounces, or 4320 grains, but as the fubftance 

 which lie obtained was not pure water, there mult be fome 

 deduction made from it on this account. We are not in- 

 formed what proportion the water bore to the mucus dif- 

 iolvedin it. Surgical Effays, pt. 1. 141. 



The difficulty of actually colleding and weighing the 

 pulmonary exhalation, is probably the caufe which induced 

 .Lavoilier in his experiments upon refpiration, to afcertain its 

 quantity by a calculation, founded upon the proportion 

 between its confhtuent parts, compared witli the compofi- 

 tion of the other fubftances which are received into and 

 difcharged from the lungs. He firil determined by direct 

 expenment the quantity of oxygen confumed, and of car- 

 bonic acid produced ; the compoiition of carbonic acid is 

 known, and by comparing the oxygen which had difap- 

 peared with the quantity which would have been neceffarv 

 to form the acid, lie found that the oxygen confumed was 

 more than fufficient to compofe the carbonic acid which 

 was actually produced. He fuppofed that this fuper- 

 abundant quantity of oxygen was employed in the formation 

 ot water, by uniting in the lungs with a portion of hydrogen • 

 he eftimates the amount of tiie water by knowing what 

 quantity of it a given weight of oxygen can produce. 



In the firft memoir (1789), the quantity of water emitted 

 from the lungs cf a man in 24 hours, is ftated to be no more 

 than 337.18 grams. In the 2d (179c), this quantity is 

 railed to 1 1 180.57 grains, or nearly 2 lbs. troy : and in the 

 laft experiments recorded by La Place, the quantity is (till 

 more confiderable, «.. 13704 grains. The proportion 

 between the water and the carbonic acid is very various 

 in theie different refearches : in the firft they are refpec- 

 tively 337.18 grains, and 17720.89 grains, or as 19 to 

 1000 nearly: m the fecond, 1 1 188.57 and 8450.24, or as 

 1323^0 1000; and in the third, 13704 and 755C.40, or 

 as 1815 to 1000. Such difcordant refults can have no 

 other effect than that of diminifliing our confidence in the 

 whole of them. 



Mr. Murray breathed into a bladder containing acetate 

 of potafh, a very deliquefcent fait, and calculated The quan- 

 tity of vapour expired by the increafe of weight in the 

 bladder and its contents, after the expired air had cooled 

 In this way he inferred that three grains of watery vapour are 

 expelled from the lungs in a minute. Sylt. of Chemittry 

 v. 4. p. 497. » 



There are two ways of explaining the produaior. of the 

 watery vapour expelled from the lungs : by evaporation of 

 the mucous fluid covering the inner furface' of the air-tubes 

 and veficles by the conftant pallage of the air to and from 

 thefe parts, which are kept at a temperature of about 98 ; 

 or by exhalation from the pulmonary or bronchial bfood- 

 veflels. The fecretion of the mucous membrane of the 

 lungs mult undergo evaporation, under the circumftances of 



