' ]g2 **R, BtlANDE's VIEW OF THE 



of carbonic acid, Lavoifier has eftimated the quantify of this 

 gas thrown out from the lungs in 21 hours, at about 15.5 

 ounces troy. Mr. Davy makes (he quantity thrown out in tlie 

 about one cubic fame time, amount to 37 ounces, which is about I cubic inch 

 inch wch expi- ^^ every expiration *. The quantity liowever varies from 0.5 

 cubic inch to 1.5 at different times in the fame perfon, fo that 

 But this varies, this accounts for the great variation in the above-mentioned 

 experiments. Moreover the proportion varies, in the fame 

 individual, during the 2-1- hours ; for I have found the quan- 

 tity of carbonic acid gas emitted from my own lungs, to be 

 rather lefs in the morning than towards the evening ; but this 

 alfo varies in different people. 

 Aqueous vapoor ^ut watery vapour is alfo emitted in refpiratioh, the greatefl: 

 alfo emitted-, ^^^^ ^p which is probably given ofT by the exhalent arteries, 

 which are fo copioufly difperfcd on the furface of the lungs. 

 A part is alfo emitted from the blood in the pulmonary veflels. 

 in quantity va- The eftimation of its quantity is attended with fome diffi- 

 "^^'^' culty ; acccording to Dr. Hales it amounts in a day to 20 



ounces : this is however but of little confequence, for it is 

 liable to' much alteration. 

 The blood un- More important changes however than thofe juft mentioned 

 ■dergoes impor- ^j-g produced by Kcfpiration, namely, the alterations produced 

 during refpira- in the blood; which fluid, returning from every part of the 

 *^°"* body by the veins, is poured into the heart; from whence, 



being propelled through the lungs, it is brought into contact 

 with the air, undergoing certain changes which render it fit 

 for the nourifbment and fupport of the body. Thefe changes, 

 which are of a very complicated nature, have engaged the 

 attention of feveral learned and ingenious philofophers. Dr. 

 It abforbs ab-j Thomfon has enumerated them as follows: 1 . The blood ab- 

 becumes florid ^^^^^ ^j^^ 2. It acquires a florid red colour, and the chyle dif- 



red ; emits car- , / .... , , , 



bonic acid; and appears. 3. It emits carbonic acid, and perhaps carbon. 4. 



water; and per- J ^ ^j^^j^s water, and perhaps hydrogen. Dr. Prieftley, M. 

 *^ ' Lavoifier, and Lagrange, have each adopted a different the- 



Varioustheories. ory, by which they endeavour to explain and account for thefe 

 changes produced by refpiration : they are all however liable 

 to confiderable objedions, and refl merely on the fuppofition 

 that the oxigen is alone abforbed. Now Mr. Davy has 

 ftiewn, that at leaft a portion of the azot difappears in the 



* 'Duvy's Refearches, page 433. 



lungs ; 



