242 THE PHYSIOLOGY OF MUSCULAR WORK 



percentage of carbon dioxide. The following are examples of 

 the results obtained : 



Composition of Mixture in Spirometer at Breaking Point. 



The complexity of muscular dyspnosa is shown by the fact 

 that it does not increase if the exercise be continued, but on the 

 contrary decreases. This is well known to athletes. During the 

 first quarter of a mile run the hyperpncea increases until panting 

 and distress are experienced, but if in spite of the discomfort the 

 run be continued the difficulty of breathing disappears and the 

 exercise can be maintained with comfort at the same or even at a 

 greater pace. The runner has now " got his second wind." This 

 interesting phenomenon has not been thoroughly investigated, 

 but it would appear that the distress is associated with a high 

 respiratory quotient, with a relative deficiency of oxygen ( 42 ). 



Composition of Alveolar Air before and after the Advent of 

 " Second Wind." 



