174 Metabolism of Healthy Man. 



preceding diet, in minor muscular activity, and, in experiments where no food 

 is taken, to the previous storage of glycogen, seems to be quite clear. The 

 influence of the ingestion of food upon metabolism has been the subject of a 

 large number of experiments in the laboratory at Wesleyan University and 

 in the Nutrition Laboratory at Boston. 



Aside from the influence of minor muscular activity, the state of digestion 

 and temperament of the individual, even during periods of the day when both 

 the minor muscular activity and the digestion are at a minimum, there further 

 exist marked differences in the amounts of carbon dioxide excreted by different 

 individuals. This is true even when the results are computed on the basis of 

 per kilogram of body-weight or per square meter of body-surface. These differ- 

 ences are especially well shown during the night periods, and the results are 

 so at variance that it seems to be clearly shown that the carbon-dioxide excre- 

 tion, as such, can not be considered as a constant quantity. What influences 

 the carbon-dioxide production during sleep is at present only a matter of 

 speculation, although the proportion of the active mass of protoplasmic tissue 

 probably plays an important role. The results of a number of unpublished 

 experiments which were made 12 hours after the last meal show that the 

 previous store of glycogen may play an important role in the carbon-dioxide 

 production during the night. 



With some individuals there is a large store of glycogen ; this is easily drawn 

 upon and consequently the carbon-dioxide production during the night may 

 be large. In others the store of glycogen may be small, and fat will be used 

 to supply the energy during the night periods. This is obviously not to be 

 interpreted as meaning that the energy is derived either wholly from glycogen 

 or wholly from fat in any one individual, but that the relative amounts of 

 fat and glycogen katabolized during the night may vary considerably in pro- 

 portion to the previous store of glycogen in the body of the subject of the 

 experiment. This type of apparatus, i. e., a large respiration chamber, and 

 the conditions which existed during most of the experiments here reported, 

 are not ideal for studying this particular problem, and investigations now in 

 progress in the Nutrition Laboratory will, it is hoped, throw light upon the 

 storage of glycogen during the night period and its effect upon the carbon- 

 dioxide production. Experiments of this nature are much needed, for not only 

 is the carbon-dioxide production during the night period from 1 a. m. to 

 7 a. m. of prime importance, but more especially the carbon-dioxide production 

 during the early waking hours from 7 o'clock to noon, since a large number 

 of experiments with various types of respiration apparatus have been made 

 during this period, 12 hours after the last meal, and the values thus found 

 have been used as a basis for subsequent scientific researches. 



