.368 thi: respiration 



In the first column is given the 2 used in c.c. per minute. Among other 

 things these figures indicate the actual amount of work done. In the 

 second column is given the C0 2 production in c.c. per minute. By divid- 

 ing the figures of the second column by those of the first, we obtain the 

 figures of the third column, representing the respiratory quotient. The 

 fourth column gives the CO, content of the alveolar air, and the last 

 column the total alveolar ventilation in liters per minute. 



Taking for the present the figures in the first and fourth columns and 

 postponing a consideration of the respiratory quotient, it will be noted 

 that, as the muscular work increases up to a total consumption of about 

 1600 c.c. of 2 per minute, the CO, percentage in the alveolar air 

 steadily increases. The question arises, does the alveolar ventilation 

 increase in proportion to the increase in C0 2 tension? If it does so, 

 increase in C0 2 tension in the blood can be held solely responsible for 

 the hyperpnea (i. e., a pure C0 2 acidosis) ; whereas if the hyperpnea is 

 greater than can be accounted for by the increase in C0 2 tension, other 

 acids must be partly responsible for the acidosis. By making this same 

 individual breathe atmospheres containing different percentages of C0 2 

 it was found that to produce a doubling of the alveolar ventilation it 

 required an increase amounting to 0.33 per cent of an atmosphere of C0 2 

 in the alveolar air (see also page 357). When we examine the above 

 figures during muscular exercise, however, we find that a rise in alveolar 

 CO, from 5.70 to 6.36 (i. e., 0.66 per cent) multiplied the normal alveolar 

 ventilation by considerably more than four times, whereas had it been 

 entirely due to an increase in CO,, it should not have been more than 

 three times as much. Evidently therefore, some other factor than C0 2 ten- 

 must have been responsible for the increased respiratory activity. This 

 conclusion is further confirmed by examination of the alveolar CO, 

 during very strenuous muscular effort, when a relative decrease in the 

 CO, percentage becomes apparent. 



If it is true that the exciting agency has been dependent partly on an 

 increase in the C0 2 tension of the blood, and partly on the production of 

 nonvolatile organic acids (lactic acid), we should expect that imme- 

 diately after discontinuing the muscular exercise the CO, tension of the 

 alveolar air would fall to a level distinctly below normal, that it would 

 only slowly recover thereafter, and that further exercise before the re- 

 covery had occurred would produce only a slight increase in alveolar 

 CO,. These results we should expect because of the much slower rate at 

 which the nonvolatile organic acid is got rid of from the organism, com- 

 pared with the volatile CO,. By actual experiment these suppositions 

 have been found to be correct, as is shown in the following table. 



