RESPIRATION. 



formly diffufed through all the cavities of the lungs ; and 

 therefore, that the proportions of the gas difcharged could 

 furnifh no accurate eitimate of thofe which were retained. 

 (Eli'u- p. 17—25-) But Mr. Dalton has (hewn, that hy- 

 drogen gas and atmofpheric air intermix, when the former 

 is kept in a phial above the latter, and commui icating only 

 by the fmall tube of a tobacc .-pipe ; and both in a (taw of 

 reft. (Manchefter Memoirs, vol. i. new fenes.) How 

 much mote readily then may this be cxpeet-d to take place, 

 where the gafes arecxpofedto fo large a furface, fuch great 

 agitation, and increafed temperature, a:, they muft have been 

 in the experiments of Mr. Davy. Neither is the fmall 

 quantity of air, which Mr. Davy affigns, fo incompatible, 

 as Dr. Bollock fuppofes, with the anatomical ftructure of 

 the thorax ; for if we call to mind the fpace which the heart 

 and the lungs occupy, and recoiled, that, under a violent 

 exertion, the chelt is made to contrad in every direction, 

 and more efpecially by the afcent of the diaphragm nearly 

 to the fourth or fifth rib, there is no difficulty in imagining 

 the quantity of air in the lungs, in fuch circumftances, to 

 be nearly that which Mr. Davy's experiments affign. 



From a review, therefore, of all the fads and experi- 

 ments above Hated, we venture to draw the following con- 

 clufions, as approaching neareit to the truth. Firlt, then, 

 according to Mr. Daw, the lungs contain, after a forced 

 expiration, a bulk of air equal to about 41 cubic inches ; 

 and according to the fame author and Dr. Goodwyn, they 

 contain, after a natural expiration, from 109 to 1 18 cubic 

 inches ; therefore the ftate of forced is to that of natural 

 expiration, as 41 to 118. Secondly, according to Dr. 

 Menzies, 40 cubic inches of air are received into the lungs 

 at each ordinary infpiration ; therefore the Hate of natural 

 expiration to that of natural infpiration will be as 118 to 

 158. Mr. Davv found like-wife, th.1t by a forced expira- 

 tion after a forced infpiration, he could expel from his lungs 

 190 cubic inches of air, and Dr. Menzies often found it to 

 amount to 200 inches ; therefor- the ftate of greateft ex- 

 hauftion of the lungs is to that of greateft repletion, as 41 

 to 231. But the 41 cubic inches of air, when infpired at 

 temperature 55 , occupied a bulk equal only to 32 ; and 

 therefore, by the fame rule of proportion, 190 cubic 

 inches infpired at the fame temperature, will be increafed 

 to 241.5 ; consequently, the greateft diminution of the 

 capacity of the cheft to its greateft expanfion will be as 41 

 to 241, in the cafe of Mr. Davy. But thefe numbers mull 

 be confidered as indicating proportions only, the abfolutc 

 quantities being different in different perfons. Thefe fads 

 decidedly (hew how much the volume of air in the ' 

 will, at all times, depend on the relative capacity of thofe 

 organs, on the more or lefs vigorous ftate of the expiratory 

 powers, and on the degree of voluntary exertion with which 

 the function may be performed. 



The circumftances in which the animal may happen to be 

 placed, will render this variation ftill more itrikiug. Tim 1, 

 from the experiments of Mr. Kite (On Apparent Death, 

 p. 27.29.) and Mr. Coleman (On Sufpended Refpirati 

 p. 7, et feq.), we learn, that in the aft of drowning, animal 

 are able to expel almoft all the air which th 'ir lungs con- 

 tain, by which thofe organs are brought into a ftate .,( . ol 

 laple. Dr. Goodwyn, on th.- oth r hand, found, that in 

 threi b I perfons, the lungs were expandi I almofl to 



their utmoll extent, containing 250, 262, and 272 cubic 

 inches of air (Ell'ay, p. 25.) ; and Mr. Col, 1 I obi *\ I, 

 that when, previous to their fufpenfion, lie I.e. 



trachea oi animals by a ligature at the mftant an inf] 



was made, in lefs than four minutes they eeai 



though the whole of the air was confined within the li 



and no obltrudion to the pallage oi the blood exilled from 

 their collapfe (p. Ill — 138). Dr. Baillie alfo has often 

 obferved the lungs filling the cheft, and diftended with air 

 and mucus, in perfons who have died aft lunatic ; fo that to 

 die and to expire are by no means lynonimous terms, — an 

 observation long fince made by Mayow, who remarked, 

 that if air be dra*vn into the lungs, and the mouth and 

 noftrils afterwards clofed, " quamvis inflati maneant pul- 

 mones, mori tamen neceife crit, quia 11011 licet expirare." 

 (Tradat. Quinquc, p. 300.) If indeed we refled, that 

 during fubmeriion in water no frefh air can enter into the 

 lungs, but that all which they contain may freely efcape; 

 and if we coulider, that before fufpenfion by the neck in 

 the human fubjed, a deep infpiration, under the influence 

 of fear, as Dr. Goodwyn obferves, is made, and that no 

 air car. afterwards pafs out, if the cord completely clofe up 

 the trachea ; it is reafonable to exped, that this variation 

 in the bulk of air contained in the lungs fhould obtain, under 

 the very different circumftances in which refpiration is 

 brought to a (land. 



How much the compofition of the air itfclf, and the 

 manner in which it is breathed, will vary the bulk of refidual 

 air in the lungs, we may colled from the experiments of 

 various authors. Dr. Hales moiitened a bladder, and fixed 

 to it a foffet, both of which would contain 74 cubic inches 

 of air. Having blown up the bladder, he put the fmall end 

 of the foffet into his mouth, and, at the fame time, pinched 

 his noftrils clofe, that no air might efcape through them, 

 and he then breathed to and fro the air contained in the 

 bladder. In lefs than half a minute, he found a confiderable 

 difficulty of breathing, and was forced after that to draw 

 his breath very fait ; and at the end of the experiment, the 

 fuffocating uneafinefs was fo great as to oblige him to take 

 away the bladder from his mouth. Towards the end of the 

 minute, the bladder was become fo flaccid that he could 

 not blow it above half full, with the greateft expiration that 

 he could make. (Statical Effays, vol. i. p. 238.) When 

 alfo Mr. Davy refpired atmofpheric air in a natural manner, 

 he tookin, he fays, only 13 cubic inches and expelled 12.7, 

 fo that only about V-rd part of the original bulk was re- 

 tained ; when he made one refpiration of 100 cubic inches 

 of air, the diminution was to 99, or -,,',,; when, after a 

 complete exhauilion of his lungs, he refpired 141 cubic 

 inches of air, once only for one-fourth of a minute, they 

 were reduced to 139, or r ' n th nearly ; and when 1G1 cubic 

 inches were breathed for about a minute, their bulk was di- 

 miiiiihcd to 152, or -,\,th (Refearches, p. 432— 435.) ;— in 

 every cafe, the diminution augmenting with the repetition 

 of the refpiration, and confequent impurity oi the air, and 

 diilrelsof the relpiratory organs. So likewile, v.hen Dr. 

 Henderfon breathed from and into the gnfometer 600 cubic 

 inches of air for four minutes, they were reduced to 57c, 

 or loll .\thof their bulk; and he adds, that he held oil 

 - ring until the fenfe of oppreilion about the cheft obliged 

 him to delilt. (Nicholfon's Journal, May 1 S04. ) Thefe 

 dill reding fymptoms, brought on by the repealed breathing 

 of the fame quantity of air, were felt in a ftill greater degree 

 by Mr. Kite; for on refpiring 591 cubic inches of at- 

 mofpheric air from and into a bladder, he experienced, in 

 one minute, great anxiety al m half a 



minute more Irani.' intolerable; his face fwelled, be< 



bl 1. X, md felt ( . Hfr ly hot, an. I fpai I 



before him ; lofs of Sght, " ! COrtfufii 



fenfes fuccei led; ind I .!.■ end of little more than two 



mini.: I II back into a chair. He was relieved by 



1. air, but remained confufed ami giddy (Eflay on 

 Apparent Death, p« 25-) The amount of the diminution 



oi 



