A manual of public health / by A. Wynter Blyth.

  • Blyth, Alexander Wynter, 1844-1921.
Date:
1890
Catalogue details

Licence: Public Domain Mark

Credit: A manual of public health / by A. Wynter Blyth. Source: Wellcome Collection.

    89/775 (page 60)
    -t- rnent of heat; oxygen unites with carbon, and carbon dioxide is formed. This absorption of oxygen and expiration of carbon dioxide is quite independent of atmospheric pressure. On the other hand, whether less or more nitrogen is absorbed is intimately con- nected with the height of the barometer. If the barometer sinks, nitrogen escapes from the_ b„ody; until equilibrium is restored ; if the barometer rises, then a certain absorption of nitrogen appears to take place. There is also a considerable expiration of aqueous vapour. (33) Composition of Expired Air. Expired air then is deficient in oxygen, is rich in carbon dioxide and in moisture. It also contains very often organic volatile bodies, such as ether and gases derived from food or drink consumed, and it is not unfrequently somewhat ammoniacal. A persons' breath smells of ether after taking alcohol, the expired air will blacken silver after eating eggs, and eructations of marsh gas are known to occur in some forms of indigestion. The healthiest person's breath also contains other forms of organic matter, the exact nature of which is obscure.1 The most recent researches show that the breath is singularly free from micro-organisms, the lungs acting as a very efficient filter. The content of carbon dioxide in expired air varies according to body weight, to age, and other circumstances, such as activity or rest. It may be taken generally as 5 per cent, of the volume of the expired air in the case of an average-sized man doing ordinary work. Speck, in 41 experiments made on his own breath under different conditions, found a maximum of 5*43 per cent, and a minimum of 333 per cent., while the oxygen also varied from 15-01 to 17-21 per cent. Pettenkofer and Voit made some very elaborate researches on the amount expired of oxygen, moisture, and carbon dioxide, of two healthy persons, during the 24 hours, under very different conditions of food and labour. 1 R. Wurtz {Oomptes Rend., cvi. 213—214) drew the air expired from the lungs through a 1 per cent, solution of oxalic acid. He found ammonia to be the chief product; but besides this, isolated a base the hydrochloride of which had a peculiar odour, and formed crystallizable soluble salts with the chlorides of gold and platinum.