1891.] Chemical Phenomena of Human Respiration. 103 



III. " On the Chemical Phenomena of Human Respiration while 

 Air is being re-breathed in a closed Vessel." By WILLIAM 

 MARCET, M.D., F.R.S. Received January 3, 1891. 



In June, 1889, I had the honour of communicating a paper to the 

 Royal Society, which appeared subsequently in the ' Philosophical 

 Transactions ' for 1890.* In this paper it was shown that the volumes 

 of air breathed to form in the body and expire a given weight of 

 carbonic acid exhibited a distinct tendency to fall with a local sub- 

 sidence of atmospheric pressure, and vice versa. Since then an 

 additional series of experiments, to which my present assistant, 

 Mr. E. Russell, kindly submitted, confirmed this result. Fifteen 

 experiments were made from to 2 hours after a meal, and fifteen 

 also from 2 to 4 hours after a meal. The results are disposed as 

 follows, in the form of a chart (see next page), in which the curves 

 for the volumes of air breathed to expire 1 gram CO 2 are seen to fall 

 most distinctly from nearly 767 mm. pressure to 742 mm. 



The object of the present investigation was to ascertain the effects 

 produced on the chemical phenomena of respiration byre-breathing a 

 given volume of air for a given time, and I gladly acknowledge the 

 valuable aid of my assistant, Mr. Edward Russell, F.C S., in the 

 course of this inquiry. It was obvious that I could not risk the 

 health of those who, together with myself, submitted to experiment ; 

 hence the necessity of limiting the duration of the time for re-breath- 

 ing air, and I selected for this purpose a period of five minutes. A 

 certain volume of air to be re-breathed was settled upon from the 

 beginning, and it was decided to take 35 litres, measured under atmo- 

 spheric pressure with every care. This air was held in a bell-jar of a 

 capacity of 40 litres, and supplied with a scale, a thermometer, and an 

 oil-gauge ; it was maintained in suspension by a counter-poise, while 

 immersed in a trough full of salt water. The bell- jar was, moreover, 

 possessed of a regulating apparatus, keeping it in perfect equilibrium 

 in every position, as it rose or fell in the tank. 



Four persons submitted to these experiments. I head the list, with 

 six complete experiments. Next, my assistant, Mr. Russell, had ten 

 complete experiments made upon himself ; a former assistant, Mr. 

 Hoskins, F.C.S., in accordance with my request, kindly submitted to 

 eleven experiments, and, finally, W. Alderwood, my laboratory 

 attendant, who has been in my service for seven years, and is well 

 qualified for this kind of work, had ten experiments made upon him. 



* ' Phil. Trans.,' B, 1890, " A Chemical Inquiry into the Phenomena of Humun 

 Respiration." 



