410 OF RESPIRATION. 



per hour; consequently in one second about 90 cubic feet, in one minute 

 5400 cubic feet, and in one hour 324,000 cubic feet of air flow over one 

 person in the open. In experiments made in France in connection with the 

 construction of the Hopital Lariboisiere with a ventilation of 350 cub. feet per 

 bed per hour, the smell was so bad, that the authorities at once directed the 

 quantity to be doubled ; but then also the state of the air was anything but 

 desirable, and it was only when the amount reached 2120 cubic feet per 

 hour that the air was found to be free from perceptible taint. Pettenkofer 

 and Voit therefore conclude that this amount of fresh air per bed per hour, 

 representing T g th of the air flowing over the body in the open, is necessary 

 for the due ventilation of hospitals, school-rooms, etc. Petteukofer and 

 Voit 1 found that no discomfort was experienced from long exposure to an 

 atmosphere containing 10 parts of carbonic acid in 1000 parts, providing 

 this had been added to the air in a pure state ; but if the same quantity were 

 present as a result of the respiration of several people, serious inconvenience 

 was soon felt ; and similarly Dr. Snow observed that the presence of carbonic 

 acid in the atmosphere acts more deleteriously upon the system in propor- 

 tion as the normal quantity of oxygen is reduced. Thus various birds and 

 mammals introduced into an atmosphere containing only from 10^-16 per 

 cent, of oxygen soon died, although means were taken to remove the car- 

 bonic acid set free by their respiration as fast as it was formed, whilst an in- 

 crease in the proportion of carbonic acid to 12 or even 20 per cent. the per- 

 centage of oxygen being kept to its regular standard of 21 per cent. did 

 not appear to enfeeble the vital actions more rapidly than did the reduction 

 of the oxygen in the experiments just referred to. Bernard 2 moreover found 

 that a bird which lay exhausted from breathing in a limited quantity of air, 

 recovered itself when the carbonic acid was partially absorbed by caustic 

 potash. He observed also that the circulation of blood charged with car- 

 bonic acid, rapidly arrested the activity of the secretory organs, as the kid- 

 neys, which recommenced to discharge their function as soon as oxygenated 

 blood was allowed to pass through them. The proportion of carbonic acid 

 present in the air of large towns has been examined by Dr. Roscoe, 3 by Dr. 

 Angus Smith, 4 and by Mr. Leigh. Dr. Roscoe found the usual proportion 

 of carbonic acid in the air of London to be 3.7 parts in 10,000; whilst the 

 proportion in Manchester, according to Dr. Smith, was 12 parts in 10,000, 

 on a still day, and from 4.5 to 8 parts in 10,000 on a windy day. From 

 experiments made with permanganate of potash, he ascertained that on the 

 high grounds north of Manchester there existed but 1 grain of organic matter 

 in 200,000 cubic inches of air, whilst in close places in the town there was 1 

 grain in 8000 cubic inches. According to Bracounot, 6 the black particles 

 always floating in the atmosphere of large towns consist chiefly of carbon, 

 bitumen, and sulphate of ammonia. Mr. Leigh finds a small quantity of 

 sulphu retted hydrogen in the air of Manchester. The air of sewers, and 

 generally air loaded with organic matters, has an alkaline reaction, from the 

 presence of ammonia and ammonium-sulphide. The numerous researches 

 that have been undertaken both in this country and abroad, especially those 

 by Pettenkofer, show that the poison both of cholera, and of typhoid, and 



1 An abstract of these observations will be found in the Med. Times and Gazette 

 for 18(32, p. 459. 



2 Bui-nurd, Liquides de 1'Organism, 1859, vol. i, p. 505. 



3 Qiinricrlv Journal of the Chemical Society, 1857; and Med.-Chir. Keview, 1861, 

 p. 4'29. 



4 On the Air of Towns, quoted in Med.-Chir. Rev., 1861, vol. ii, p. 433. 



5 See Twenty-ninth Annual Report of the Regist. Gen , 1868. 



6 Animl. de Chimie et do 1'hys., t. xxxiii. 



