1889.] 



into the Phenomena of Human Respiration. 



343 



the influence of food and changes of atmospheric pressure on the 

 volume of air breathed and weight of C0. 2 expired. Two persons, 

 my assistant, Mr. C. F. Townsend, and my laboratory attendant, 

 William Alderwood, kindly submitted to experiment. 



The person under experiment sat in a semi-recumbent posture in a 

 deck-chair, with his feet resting on a stool, so as to do away with all 

 muscular effort. He inspired by the nose only, and expired through 

 the mouth into a wide india-rubber tube, connected with a bell- jar, of 

 a capacity of over 40 litres, and suspended over salt water. The 

 bell-jar was accurately counterpoised over a pulley fixed to a cycloid, 

 whose leverage power, increasing as the bell-jar rose, kept the latter 

 perfectly balanced, -and therefore the air it contained was under 

 atmospheric pressure in every position. The time for collecting the 

 air expired was measured with a stop watch. In order to make sure 

 of no air being expired accidentally through the nose, at the end of 

 each inspiration the nose was closed with the index-fingers, and thus 

 held during the expiration. 



In order to obviate the objection that the attention given to the 

 experiment might interfere with natural breathing, the air was 

 expired into the bell- jar through a double-way cock, disposed in such 

 a manner that the person under experiment might, unknown to him, 

 either expire into the external air or into the bell-jar. At the com- 

 mencement of the experiment he was made to expire into the open 

 air, and when, after ten minutes or a quarter of an hour, his respira- 

 tion had become perfectly regular, the stopcock was turned a.nd the 

 air admitted into the bell-jar. The latter was so well suspended that 

 it rose without the least effort ; thus, the person experimented upon, 

 unless looking at the bell-jar, could not tell whether he was breathing 

 into it or into the external air. 



The carbonic acid was determined by aspiring with a pump the air 

 from the bell-jar into a glass cylinder of a capacity qf 1000 c.c, to 

 which was subsequently screwed, air-tight, a bottle holding 100 c.c. of 

 a normal solution of barium hydrate. After agitating the air with the 

 akaline solution for a minute or two, about 100 c.c. of common air free 

 from C0 2 , and contained in a pear-shaped india-rubber bag, was forced 

 into the cylinder by pressure with the hand, and then the shaking 

 resumed for a quarter of an hour. The addition of the air caused a 

 pressure inside the cylinder which was found to accelerate greatly the 

 combination of the C0 2 . Finally, the alkaline solution was decanted 

 into a glass-stoppered bottle of a capacity of about 100 c.c, amd the 

 stopper secured with paraffin. The morning of the next day, when 

 the precipitate had entirely subsided, the clear fluid w 7 as titrated with 

 a standard solution of oxalic acid in the usual way. 



A number of precautions were taken to insure the accuracy of the 

 method; perhaps the most important was blowing, with a bellows, a 



