The Composition of Expired Air, and its Effects upon 



Animal Life. 



REPORT ON THE RESULTS OF AN INVESTIGATION MADE FOR THE SMITHSONIAN INSTI- 

 TUTION UNDER THE PROVISIONS OF THE HODGKINS FUND. 



By J. S. Billings, M.D., S. Weir Mitchell, M.D., and D. H. Bergey, M.D. 



la May, 1893, a grant was made from the Hodgkins Fund to Di's. John S. 

 Billings and S. Weir Mitchell, "for the purpose of conducting an investigation into 

 the nature of the [)eculiar substances of oi'ganic origin contained in the air expired 

 by human beings, with special i-eference to the practical application of the results 

 obtained to pi'obleras of ventilation for inhabited rooms." 



For a numbei- of years prior to 1888 the prevailing view among physicians and 

 sanitarians had been that the discomfort and dangers to health and life which had 

 been known to exist, sometimes at least, in unventilated rooms occupied by a num- 

 ber of human beings, were largely or entirely due to peculiar organic matters con- 

 tained in the air expired by these pei'sons, and that the increase in carbonic acid 

 due to I'espiration had but little effect in producing these results, its chief import- 

 ance beina; that it furnished a convenient means of determininc: the amount of 

 vitiation of the air. Recently, however, several experimenters have concluded that 

 the organic matters in the exhaled bi'eath are not harmful, at .ill events to animals, 

 and the main object of the proposed investigation was to determine the correctness 

 of these conclusions. Foi' this purpose a scheme of experimentation was prepared 

 by Drs. Billings and Mitchell, whicli scheme has been carried out in the Laboratory 

 of Hygiene of the University of Pennsylvania, by Dr. D. H. Bergey, assisted at 

 times in the chemical work by Di'. Hill S. Warwick, and in some of the pathological 

 investigations by Dr. Ingersoll Olmsted, and under the general supervision of Dr. 

 A. C. Abbott, First Assistant in the Laboratory, to whom thanks are due for many 

 valuable suggestions during the progress of the work. From time to time Dr. 



