392 Curve of Carbon-dioxide Excretion [April 



before the beginning of forced breathing; the line Pqq'q"r (broken 

 by the arresting of the beam and the addition of foiir gram weights) 

 represents the curve of carbon dioxide during forced breathing; r 

 is the Position on the curve of the carbon-dioxide-writing lever at 

 the instant when work was begun ; and s is the point where the curve 

 changes as a residt of the zvork. 



This research was conducted on two subjects. It was found 

 very difficult to maintain respiration of uniform depth for five 

 minutes, since there is a decided tendency to make the respiration 

 shallower. Indeed, notwithstanding the great care on the part of 

 the subject, the Pneumograph record indicated, in some cases, a 

 lessened depth of respiration toward the end of the forced respira- 

 tion period. 



In the case of one subject the curve for rate of excretion of 

 carbon dioxide returned, during the period of forced respiration, 

 practically to the original value. With the other subject the return 

 was less perfect, It would seem that as a result of the additional 

 work of the respiratory Organs a return of the rate of excretion to 

 the value during normal respiration could not be expected. 



While, therefore, the writer is able to confirm Prof. Zuntz's pre- 

 diction regarding the sharpness of the change, as a result of work, in 

 the curve of carbon dioxide after continued forced respiration, he 

 can confirm only in part Prof. Zuntz's prediction on the return of 

 the curve, during forced respiration, to the direction which it had 

 before forced respiration was begun. 



This work was done in the physiological laboratory of the Uni- 

 versity of Michigan, Ann Arbor, Michigan. 



