502 Dr. W. Marcet on the Function of Respiration at [Apr. 24, 



The air from the lungs was expired into a strong india-rubber bag 

 •of a known capacity under a pressure of one inch of water. The 

 bag used in nearly every experiment sitting held 39*8 litres of air under 

 that pressure ; and in the experiments made while engaged with a 

 measured amount of muscular work, a bag holding 68 '4 litres of air 

 under the same pressure was employed. 



The tube into which the expired air was drawn for analysis was 

 supplied with the india-rubber diverticulum described in my former 

 communication, and I made occasional use of it to take out small 

 ■quantities of air and test them with a solution of barium hydrate. I 

 thus observed that a continued agitation of five minutes sufficed for 

 the entire combination of the carbonic acid. In every experiment the 

 -agitation was continued for six or seven minutes or longer, by the 

 watch. The bottles, into which the fluid was drawn after agitation, 

 were well corked, and their necks dipped into melted paraffin. 

 Although large enough for somewhat more than the bulk of the fluid 

 they contained, the empty space was too small for the air it held to 

 affect the alkaline solution. 



My Chamounix guide was practised in the mode of breathing into 

 the bag, so that I could rely upon his doing this in a perfectly natural 

 way, and without the loss of any of the air expired ; he was also in 

 the habit of counting his expirations while so engaged. 



We assisted each other mutually ; one of us keeping an eye on the 

 stop-watch and the bag, while the other was breathing into it. 

 After sitting quiet for a few minutes, the mouth was applied to the 

 mouthpiece, and at the very beginning of the first expiration, a sign 

 was made and the stop-watch started. When the bag was nearly 

 full, the water in the gauge began to rise, and the instant it attained 

 the height of one inch, the watch was stopped. The time to fill the 

 bag was then read off, and the temperature of the air in the bag 

 ascertained, both observations being immediately noted. Without 

 ;any loss of time the air was at once aspired into the cylinder, and its 

 temperature within the cylinder again read off by means of a thermo- 

 meter run through the india-rubber stopper. 



Then followed the introduction of the normal alkaline solution, 

 the agitation and the bottling ; a whole experiment took from thirty 

 minutes to forty-five or fifty minutes. The total number of my 

 Teneriffe experiments on respiration, including the determination of 

 the carbonic acid expired, amounted to 157. 



The Chamounix guide is a tall and very powerful man of 38 years 

 •of age ; I found him to measure round the bare chest at the nipples, 

 3 feet 5 inches. His height, in boots with moderately thick soles, 

 is 6 feetO^ inch, and he subsequently found his weight to be 89 kilog., 

 — exactly 14 stone, 



I am 50 years of age, measure 2 feet 10^ inches round the bare 



