WORK PRODUCTION 



541 



the protein katabolism have already been cited (636) but may 

 be repeated in connection with those obtained with the aid of 

 the respiration apparatus. 



TABLE 154. INFLUENCE OF WORK ON GASEOUS EXCHANGE OF MAN 



639. Effects are immediate. Experiment confirms the com- 

 mon observation that the increased pulmonary exchange conse- 

 quent upon muscular exertion begins almost immediately, 

 reaches its maximum in a very short time and disappears 

 promptly when the work ceases. This is especially true of the 

 absorption of oxygen, of which no considerable amount ap- 

 pears to be stored up in the body in the free state. In the case 

 of the excretion of carbon dioxid, more or less of this gas can 

 be held in solution in the blood and lymph and there is conse- 

 quently some slight lag in its excretion. 



In view of this prompt adjustment of the respiration to the 

 amount of work, determinations of the pulmonary exchange by 

 some one of the forms of respiration apparatus described in 

 Chapter VI (297-299) are especially useful in studying the effects 

 of work upon the katabolism. The use of this method renders 

 it possible to compare the gaseous exchange during periods of 

 work with that of the same animal at rest and thus to deter- 

 mine very sharply the additional oxygen consumption and 

 carbon dioxid excretion caused by a measured amount of 

 work. The comparative simplicity of the apparatus required, 

 the ease with which the respiratory changes can be followed in 

 short periods, and the fact that both oxygen and carbon dioxid 



