104 



Dr. W. Marcet. 



2"- 



The results obtained for Mr. Floris were as follows : 



There can be no doubt, therefore, that the excess C0 2 expired in 

 forced breathing is a result of diffusion through the moist pulmonary 

 membrane of some of the C0 2 stored up in the blood. Forced 

 breathing is concerned in sighing, yawning, and sneezing. 



Breathing under Muscular Exercise. 



The third form of breathing is under muscular exercise when an 

 increased volume of air is breathed and a larger volume of C0 2 

 expired than in a state of repose. It has been shown in my last 

 paper that the mean volume of oxygen, absorbed (not transformed 

 into CO 2 ), at all events within a few minutes (from 15 to 18 minutes) 

 after exercise has commenced, is the same as in the state of repose, 

 or nearly so ; this I have confirmed by more recent experiments, 

 which, however, are not included in the present work. The increased 

 action of the respiratory muscles under exercise is involuntary, un- 

 attended with fatigue, and differs in these respects from forced 

 breathing. Again, in muscular exercise there is no apncea or reaction 

 after the exercise is arrested; on assuming a state of repose the 

 breathing continues for a short time much the same as during 



