RESPIRATION. 



355 



From the details given above we may ob- 

 tain information of considerable importancn 

 on several practical points. A consideratioe 

 of the large quantity of atmospheric air pass- 

 ing through the lungs in the 24 hoars, and 

 the extent to which it is vitiated by this in the 

 removal of a part of its oxygen and the sub- 

 stitution of a quantity of carbonic acid gas, 

 will assist us in acquiring definite information 

 regarding the amount of ventilation required 

 in the apartments of our private and public 

 buildings. It appears that between 400 and 

 500 cubic feet of atmospheric air pass daily 

 through the lungs of an adult enjoying mode- 

 rate exercise; and the estimate of Dalton, 

 that 23 cubic feet of oxygen gas are, during 

 the same period, aborbed at the lungs, is pro- 

 bably not far from the average. The same 

 air cannot be breathed twice without in- 

 ducing prejudicial effects, so that at each in- 

 spiration entirely fresh air ought to be sup- 

 plied, or the air already breathed ought to be 

 so largely diluted by the admission of fresh 

 air as to be restored very nearly to its original 

 composition. Leblanc informs us, that in the 

 Chamber of Deputies in Paris, where the 

 system of ventilation is based upon the prin- 

 ciple of furnishing to each individual from 10 

 to 20 metres cubes (353'316 to 706331 

 English cubic feet) of air per hour, the air 

 issuing from the apartment contained from 

 2 to 4 of carbonic acid gas in the 1000 parts 

 by weight.* The quantity of pure atmospheric 

 air here furnished is probably somewhat insuf- 

 ficient, if the presence of 1 part of carbonic 

 acid in the 100 of atmospheric air be likely to 

 act prejudicially when breathed for a long time 



* Annales de Chimie et de Physique, troisieme 

 se'rie, torn. v. p. 241. 1842. In the Model Prison at 

 Pentonville from 30 to 45 cubic feet per minute, or 

 from 1800 to 2700 cubic feet per hour, of pure fresh 

 air is made to pass into every cell. (Report of the 

 Surveyor-General on the Construction, &c. of Pen- 

 tonville Prison. 1844.) 



continuously. From Dr. Snow's experiments, 

 it appears that the prejudicial effects of breath- 

 ing air deteriorated by respiration, is not en- 

 tirely due to the presence of an increased 

 quantity of carbonic acid gas, but also in a 

 considerable degree to the diminution of the 

 oxygen. He found that birds and mammalia 

 introduced into an atmosphere containing 

 only from 16 to 10i per cent, of oxygen soon 

 died, though means were adopted for remov- 

 ing the carbonic acid formed by respiration.* 

 The increase of the carbonic acid gas to 12 

 and 20 per cent., provided the oxygen gas was 

 still as high as 21 per cent., did not appear to 

 enfeeble the vital actions more rapidly than 

 the diminution of the oxygen to the extent 

 above stated. Any notable diminution in the 

 percentage of the oxygen gas, even when no 

 carbonic acid is present, cannot take place 

 without danger to the warm-blooded ani- 

 mals -|-, and the carbonic acid in the air 

 respired acts more or less energetically in 

 destroying life, as it has been produced at the 

 expense of the oxygen of the air, or been 

 added to it already formed .J 



* Edinburgh Medical and Surgical Journal, vol. 

 Ixv. 1846. A green-linnet was confined in a vessel 

 containing 2000 cubic inches of air, consisting of 16 

 of oxygen and 84 of nitrogen in the 100 parts by 

 volume, and it died in ten minutes. A mouse was 

 introduced into the same vessel filled with air con- 

 taining 10 per cent, of oxygen, and in five minutes 

 it was no longer able to stand. 



f There is a marked difference in this respect be- 

 tween the cold-blooded and warm-blooded animals. 

 Vauquelin (Annales de Chimie, torn. xii. p. 271. 1792) 

 in his experiments upon some snails, found that 

 when confined in a quantity of air, all the oxygen 

 had disappeared at the time of their death ; and 

 Spallanzani observed the same thing in a few of his 

 experiments on the same animals. Matteucci (Le- 

 9ons sur les Phenomenes Physiques des Corps Vi- 

 vants, p. 115. 1847), obtained similar results on a 

 torpedo confined in a limited quantity of water. 



| Dr. Snow infers from his experiments on the 

 lower animals that in the human species " five or 

 A A 2 



