1891.] Phenomena of Human Respiration. 105 



The results from all these experiments will be found disposed in the 

 form of tables (pp. 113 116). 



I shall first give a short account of the method adopted in the pre- 

 sent inquiry, then describe the experiments, and finally state the 

 results with which they have been attended. Two bell-jars were made 

 use of. 



The air, in every one of the experiments quoted in this paper, was 

 inspired through the nose and expired through the mouth, a mode of 

 breathing easy to acquire, and soon becoming perfectly natural ; the 

 person under experiment assumed the recumbent position in a deck- 

 chair, with the feet resting on a stool. 



It was necessary to begin by determining the volumes of air and 

 weights of carbonic acid expired normally, or in ordinary breathing, 

 with the object of using 'these figures as standards for comparison. I 

 need not say that every precaution was taken to obtain correct data 

 on ordinary breathing. Next, the other bell-jar was supplied with 

 atmospheric air to be re-breathed. A correction might have been 

 introduced for the CO 2 naturally present, but from its small propor- 

 tion this correction was thought unnecessary. On no occasion was 

 the laboratory used for the evolution of acids or alkalis, and its 

 ventilation was kept up by one or two open windows. 



After re-breathing 35 litres of air during five minutes, the person 

 under experiment was placed in communication with the other bell- 

 jar, in such a manner that no air whatever was lost, or, in other 

 words, while fresh air was inspired, the expiration following imme- 

 diately the last expiration of re-breathed air was collected in the other 

 bell-jar, now emptied of the expired air it formerly contained. While 

 this bell- jar was being filled, the re- breathed air, from the other bell- 

 jar (after its volume had been read, and temperature taken), was 

 driven into an india-rubber bag faced with oil-skin, to prevent any loss 

 of any C0 2 by diffusion. This bag had been kept flattened down 

 between boards weighted with a piece of iron weighing 20 Ibs., a 

 precaution taken to empty perfectly the bag before it was used for 

 storing the re-breathed air. The bell-jar, having thus discharged its 

 contents, was ready to be used afresh. 



The person expired from 34 to 38 litres of air immediately after the 

 re-breathing stage of the experiment, and he was now placed in com- 

 munication with the empty be 11- jar ; there was no loss of expired air 

 through this passage from one bell-jar to another, and while fresh air 

 was inhaled, the air expired was entirely collected, to the extent of 

 from 34 to 38 litres, for subsequent analysis. A chronograph showed, 

 to a second, the time required in the various stages of the experi- 

 ment. 



Thus the whole history of the effects of re-breathing air was obtained, 

 being divided into four stages : 1st, natural respiration ; 2ndly, air 



