u 



THE COMPOSITION OF EXPIRED AIR, 



and sides of the flask. These cultures were kept under observation for 20 to 30 days, .\bout 150 



c. c. of the gelatin was used for each experiment. The glass tube, l>, of the 



\.^^X^^?=^<^ apparatus used, which served for the entrance of the expired air, was inserted 



■^-^ « T far enough to just impinge on the fluid culture medium in the flask, so that the 



air produced a slight agitation of the fluid in passing through the apparatus. 



Description of the apparatus used for determining the presence of bacteria 

 in expired breath. Fig. 1.: 1', rei)resents a half litre Erlenmeyer flask closed with 

 a rubber stopper having two openings. Each of these openings is closed by a 

 Pig. i._.\pparatus glass tube bent at right angles above the stopper, 

 for determining the ^^ represents the longer glass tube which reaches nearly to the bottom of 



I'nTxpTrcd'breat'h"" the flask. This tube has a small bulb-shaped enlargement blown into its upper 

 end, which serves to retain any saliva that might flow into the tube. This 

 tube serves as the mouthpiece through which the air enters the apparatus. When not in use, the 

 mouth-piece is closed with a small cotton plug. The internal diameter of the tube is seven mm. 



t:, the shorter tube is bent at right angles and terminates just below the stopper. The external 

 end of this tube is closed with a cotton plug to prevent the entrance of micro-organisms from this 

 side of the apparatus. The internal diameter of this tube is also seven mm. 



The organisms which developed in these cultures were all of the same character — a small 

 yellow bacillus which is quite common in the air of the laboratory. In the experiments in which 

 gelatin remained sterile, the precaution had been taken to sterilize the apparatus with dry heat for 

 an hour previous to introducing the gelatin, besides the subsequent sterilization of the culture 

 medium on three successive days. If, after standing in the working room for several days, it was 

 found that the culture medium was sterile, the expired breath was then conducted through the 

 apparatus and the culture was kept under observation (for the time specified in the table) at the 

 room temperature. The nature of the organisms that developed in the first two experiments, and 

 the absence of any growth in tli£ others, makes it probable that they developed from spores that 

 survived the fractional sterilization of the culture medium. It is improbable that they were carried 

 in the expired breath. 



Several attempts were made to use bouillon and litmus milk instead of gelatin, as the culture 

 medium. Neither of the former media was found to be suitable for the purpose. 



Careful examination of the fluid condensed from the expired air was made with high powers, 

 both in hanging drops, and in six dried and stained preparations, but nothing resembling bacteria or 

 epithelium was found. A few amorphous particles, a few minute apparently crystalline masses, 

 and here and there a fragment resembling vegetable fibre, were all that could be seen. 



II_ A series of experiments was made to determine the amount of ammonia, of albuminoid 



ammonia, and of oxidizable matters contained in the fluids condensed from expired air. 



The apparatus used in collecting the condensed vapor from expired breath is represented in 

 Fig. 2, the condenser of which is laid in ice. Each time before this apparatus was brought into 

 use, the condenser was boiled out with either a solution of bichromate of potash and sulphuric 

 acid, or with alkaline permanganate of ])Otash, then freely rinsed with twice distilled water until 

 entirely free from the cleansing solutions used. The apparatus was then quickly connected 

 together and placed in a large steam sterilizer for an hour. The condenser was then packed in 

 ice and the breath exhaled through the apparatus, using but little greater ex|)iratory force than in 

 ordinary respiration. In several of the experiments a gas meter was attached after the apparatus, 

 in order to measure the volume of air exhaled. This was found to approximate a third of a cubic 

 metre per hour, during which time as much as 12 c. c. of moisture was collected. 



The amount of air expired in ordinary quiet respiration ranges from 400 to 500 litres per hour. 

 It is evident that the diminished amount exhaled in the experiment did not represent the full 

 respiratory capacity ; the reduction observed having its cause, in all probability, in the slightly 

 greater effort required to conduct the expired breath through the apparatus. It was noted that the 

 number of expirations ranged from twelve to fifteen per minute, the ordinary rate being about 



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