1910.] WORK ON NUTRITIVE PROCESSES. 151 



tain experiment. If our chemical analyses have been accurate, 

 we should be able to compute from the fuel values of protein, 

 fat and carbohydrate thus obtained the heat these substances 

 would be expected to produce when burned in the body. Obviously, 

 this result should compare with the results as actually determined. 

 When our apparatus functionates so perfectly that we can secure 

 results in this way, we can feel that we are on safe ground and 

 our results give us a very perfect picture of what takes place in 

 the body. Having found such an apparatus and method, it only re- 

 mains for us to apply this apparatus in as many ways as time and 

 expense will permit. 



Among the numerous questions that can be solved by an appara- 

 tus of this type is the effect of work on changes in material in the 

 body, which we call metaboHsm. We know that when a man is 

 sitting quietly at rest in a chair, he gives ofif, say, lOO calories of 

 heat per hour. This is about the amount of heat given off from a 

 32 c.p. electric lamp. If, however, a man stands up and walks 

 about, we have found that his heat production rises considerably 

 and we find, also, that not only does the heat elimination increase 

 but the carbon dioxide in the breath increases correspondingly. 



Muscular exercise with varying degrees of intensity produces 

 varying amounts of carbon dioxide and heat as is shown by the table 



TABLE I. 

 Average Normal Output of Carbon Dioxid and Heat from the Body. 



Average Quantities 

 per Hour. 

 Carbon Dioxid. Heat. 

 Conditions of Muscular Activity. Cms. Cals 



Man at rest, sleeping 25 65 



Man at rest, awake, sitting up 35 100 



Man at light muscular exercise 55 i7o 



Man at moderately active muscular exercise.... 100 290 



Man at severe muscular exercise 150 450 



Man at very severe muscular exercise 210 600 



herewith. The classification of muscular exercise on this basis is 

 very unsatisfactory, as different people may have different im- 

 pressions of what is meant by "moderately active muscular exer- 

 cise," for example. It is certain, however, that under these con- 

 ditions, the characterization so far as the sleeping period is 



