402 THE COMPOSITION OF EXPIRED AIR. 



and relative humidity of the inspired air. With air containing- 50 per 

 cent of moisture inspired at 25° C, the amount of moisture is 293 grams, 

 or about the result given by Ben, referred to above. 



Lehmann and Jessen (19) found that between 3 and 4 milligrams of 

 oxygen were required in 1 liter of fluid to effect oxidation, and note 

 that more ammonia was present in the fluid collected from a person 

 with decayed teeth than in that obtained from a person whose teeth 

 were sound. The very considerable differences in the amounts of 

 ammonia and of oxidizable matter found in the fluid condensed from 

 expired air by different experimenters, and by the same experimenter, 

 in fluids obtained from the same person at different times, are probably 

 due to several different causes and their combinations. The amount 

 of fluid condensed per liter of expired air varies from 0.003 to 0.004 c. c. 

 The soundness and cleanliness of the mouth and teeth influence the 

 amount of ammonia and oxidizable matter expired. Variations in the 

 amount of organic matter contained in the inhaled air may possibly 

 influence the result, but this influence must be slight. Ransome's 

 results indicate that the age, health, and vigor of the person may affect 

 the amount of organic matter exhaled, and Dr. Bergey's experiments 

 with the fluid obtained from the consumptive patient show that a smaller 

 proportion of ammonia and a larger amount of oxidizable matter were 

 present in it than in the fluid collected from a healthy man. It should 

 be remembered, also, that it is extremely difficult to obtain accurate 

 results in quantitative determinations of such very minute amounts of 

 ammonia and oxidizable matters as are found in expired air, and a 

 part of the differences in results obtained is no doubt due to unnoted 

 differences in the details of the experiment. 



The results of tests for the presence of an organic alkaloid in the 

 condensed fluids obtained by Dr. Bergey were negative, corresponding 

 to those reported by Lehmann and Jessen (19) and by Beu (25). 



The results of attempts to condense the moisture of the air in the 

 hospital ward were not satisfactory, and the determinations of ammonia 

 in the fluid obtained are not comparable, except they show that the 

 placing of a dust filter in front of the condensing apparatus causes 

 a marked reduction in the proportion of ammonia in the condensed fluid. 

 The evaporation equaled the condensation except on days when the 

 external air was saturated with moisture, hence no moisture was col- 

 lected on clear days, but on such days some dust particles may have- 

 accumulated in the apparatus which had no filter. 



Several series of experiments were made to determine the nature 

 of the gaseous mixtures in which small animals die with symptoms of 

 asphyxia. The first of these series were repetitions of the experiments 

 reported by Hammond and described above. Mice and sparrows were 

 used. It was found impossible, by Hammond's method, to absorb all 

 the carbonic acid produced by an animal. At the time of death of the 

 sparrows, the carbonic acid had increased until it formed from 12.27 



