240 THE PHYSIOLOGY OF MUSCULAR WORK 



Effects of Work on the Percentage of Carbon Dioxide in the 

 Alveolar Air 



From these data they conclude that the hyperpncea of muscular 

 work is due to a rise in the pressure of carbon dioxide in the res- 

 piratory centre, but it is necessary to bear in mind that they 

 measured the pressure of carbon dioxide in the alveolar air, not 

 in the blood. 



The history of the different views upon the causation of the 

 hyperpncea produced by muscular work illustrates extremely well 

 those fluctuations between old and new theories which are so 

 constantly observed in the biological sciences. Muscular activity 

 increases the ventilation of the lungs, the intake of oxygen and the 

 output of carbon dioxide. It was but natural, therefore, that the 

 hyperpncea should be attributed to a deficiency of oxygen or to 

 an excess of carbon dioxide in the blood due to the greatly in- 

 creased metabolism. To these causes hyperpncea was generally 

 attributed until Geppert and Zuntz ( 36 ) found that muscular activity 

 was accompanied by an increase in the oxygen and a decrease in 

 the carbon dioxide of the blood. These observers considered that 



