THE COMPOSITION OF EXPIRED AIR. 391 



richer in oxygen than air, in which case he found that by passing 

 electric sparks from a frictional machine through the fatal air (having 

 previously deprived it of its carbonic acid) it was again made capable 

 of supporting life, from which he concluded that the oxygen is " devi- 

 talized" during respiration, and that the electric spark has the faculty 

 of revitalizing it. 



Von Pettenkofer, in 1860-18G3 (6), showed that the symptoms observed 

 in crowded, ill-ventilated places were not produced by the excess of 

 carbonic acid, nor by a decrease in the proportion of oxygen in the air ; 

 neither of these being sufficient in our dwellings, theaters, etc., to pro- 

 duce toxic effects. He did not believe that the impure air of dwellings 

 was directly capable of originating specific diseases, or that it was 

 really a poison in the ordinary sense of the term, but that it diminished 

 the capability of withstanding the influence of disease-producing agen- 

 cies on the part of those continually breathing such air, and laid down 

 the rule, which has been accepted and taught by sanitarians for thirty- 

 five years, that the proportion of carbonic acid in the atmosphere of 

 inhabited places affords a safe indication as to the amount of the other 

 impurities resulting from respiration and other exhalations from the 

 bodies of the occupants. 



Hammond, in 1863 (7), reported experiments in which he sought to 

 remove the carbonic acid and moisture, and to supply fresh air as fast 

 as it is needed to take the place of the carbonic acid removed, thus 

 leaving the "organic matter" to accumulate in the vessel. For this 

 purpose he confined a mouse in a large jar, in which were several 

 sponges saturated with baryta water, by which the carbonic acid was 

 removed as fast as formed. Fresh air was supplied as fast as required 

 by means of a tube communicating with the bell jar and closed by 

 water in the bend of the tube, which acted as a valve. As the air in 

 the bell glass was rarefied by respiration and absorption of the car- 

 bonic acid, fresh air flowed in from without, while the arrangement of 

 the tube prevented the air of the bell glass from passing out. The 

 watery vapor exhaled by the animal was absorbed by two or three 

 small pieces of chloride of calcium. The mouse died in forty minutes. 

 The observation was repeated many times, and death ensued invariably 

 in less than an hour. On causing the vitiated air to pass through a 

 solution of permanganate of potash the presence of organic matters in 

 large quantity was demonstrated. 



Eansome, in 1870 (8), reported a series of very interesting investi- 

 gations upon " Organic matter of human breath in health and disease.'' 

 By condensing the aqueous vapor of the human breath and analyzing 

 it by the Wanklyn and Chapman method, he found that "in ordinary 

 respiration about 0.2 gram of organic matter is given off from a healthy 

 man's lungs in twenty-four hours," while in the air expired by persons 

 affected with certain diseases, he found great variations in the amount 

 of organic matter, the amount being greatest in a case of phthisis com- 

 plicated with Bright's disease. 



