152 Scientific Proceedings (127) 



a 5 to 6 liter rubber bag. Starting either from full inspiration or 

 full expiration the subject rebreathes uniformly and almost as 

 deeply as possible from the bag a certain number of times. The 

 connection between the mouth and the bag is a 35 cm. long, 2 

 cm. wide rubber tube and a 3-way stopcock. The frequency of 

 respiration has always been betwen 8 and 20, usually about 10-15 

 per minute. During the experiments several small samples 

 (15-20 c. c.) of air were drawn (1) from the bag, and (2) from 

 the very last part of the expiration. In the last instance there- 

 fore, alveolar air was obtained. The samples were drawn into 

 evacuated recipients without interrupting or interfering with the 

 breathing. By such a procedure (Fig. 1) one can follow the 

 changes in the composition of the air in the two most important 

 places (bag and alveoli) of the closed system during the re- 

 breathing experiment. In the oxygen experiments the changes 

 in the nitrogen percentage were followed and in the hydrogen 

 experiments the changes in the hydrogen percentage were ob- 

 served. 



Results. In Table I an example of oxygen experiments are 

 given and in Table II an example of hydrogen experiments. 

 Figs. 2 and 3 correspond to Tables I and II respectively. 



If complete mixture is defined as a state of uniformity of com- 

 position of air in the whole rebreathing system, it is already clear 

 that full mixture cannot be obtained on account of the continu- 

 ous interchange between the alveolar air and the blood gases, 

 (the influence of respiratory quotient, of hydrogen absorption 



Fig. 1 



Five liters rubber bag. Lead tubes with capillary borings for drawing 

 samples without interfering with rebreathing. 



