Air, water and food from a sanitary standpoint / by Ellen H. Richards and Alpheus G. Woodman.

  • Ellen Swallow Richards
Date:
1900
Catalogue details

Licence: Public Domain Mark

Credit: Air, water and food from a sanitary standpoint / by Ellen H. Richards and Alpheus G. Woodman. Source: Wellcome Collection.

Provider: This material has been provided by the Harvey Cushing/John Hay Whitney Medical Library at Yale University, through the Medical Heritage Library. The original may be consulted at the Harvey Cushing/John Hay Whitney Medical Library at Yale University.

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    therefore justified, namely, that air, water, and food toge.her are three essentials of human existence. A certain relation between the three means health, and any disturbance of this relation means unhealth, by which term may be designated a condition of less than perfect health not yet so serious as to be called sickness. Air being a mere mixture of the gases nitrogen and oxy- gen, in no definite atomic proportions, and carrying varying amounts of other substances, gaseous and suspended parti- cles, no definite composition can be given. The difference between the air over sea or forest plateau and that of city streets or of crowded tenements seems only slight if expressed in per cent. From 20.98 per cent, of oxygen in the first to 20.87 and 20.60 in the last; from .022 per cent, of carbon dioxide in the purest air to .045 in cities and .33 in rooms, are the common variations; and yet the effect of these apparently sma'l differences on human beings subjected to them is very noticeable. It is customary to enhance these differences by expressing the results in parts per 10,000. That the carbon dioxide is of itself a disturbing factor is indicated by the observed fact that air which has had the per cent, of oxygen reduced by combustion to a point at which a candle will no longer burn may be made again a supporter of combustion by the removal of the carbon dioxide. A practical application of this principle is made in the devices used in diving and in entering mines filled with irre- spirable gases. There is a sensible effort in breathing, and a feeling of discomfort is usually experienced, if the carbon dioxide ac- cumulates to ten times the normal amount, or 40 parts per 10,000 instead of 4. This is probably due to its solubility and to its interference with the respiratory exchange, since the interchange of gases is influenced by their partial pres-
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