864 METABOLISM. 



IV. THE DEPENDENCE OF METABOLISM ON OTHER CONDITIONS. 



The so-called basal requirement which was previously mentioned, 

 i.e., the extent of metabolism with absolute rest of body and inactivity 

 of the intestinal tract, serves best as a starting-point for the study of 

 metabolism under various external circumstances. The metabolism 

 going on under these conditions leads in the first place to the production 

 of heat, and it is only to a subordinate degree dependent upon the work 

 of the circulatory and respiratory apparatus and the activity of the glands. 

 According to a calculation by ZUNTZ/ only 10-20 per cent of the total 

 calories of the basal requirement belongs to the circulation and 

 respiration work. 



The magnitude of the basal requirement depends in the first 

 place upon the heat production necessary to cover the loss of heat, and 

 this heat production is in turn dependent upon the relation between 

 the weight and the surface of the body. 



Weight of Body and Age. The greater the mass of the body the greater 

 the absolute consumption of material; while, on the contrary, other 

 things being equal, a small individual of the same species of animal metab- 

 olizes absolutely less, but relatively more as compared with the unit of 

 the weight of the body. With increasing bodily weight the total metab- 

 olism per kilo of animal diminishes, which is true first for individuals of 

 the same species of animals, but also seems to have a certain correctness 

 on the comparison of different species of animals. It must be remarked 

 that the relation between flesh and fat in the body exerts an important 

 influence. The extent of the metabolism is dependent upon the quantity 

 of active cells, and a very fat individual therefore decomposes less sub- 

 stance per kilo than a lean person of the same weight. According to 

 RUBNER 2 the importance of the size of the flesh or cell-mass in the body 

 is overestimated. In his investigations on two boys, one of whom was 

 corpulent, and the other normally developed, and on comparing the food- 

 need with that found by CAMERER for boys of the same weight, RUBNER 

 came to the result that the exchange of force in the corpulent boy almost 

 completely corresponded with that in the non-corpulent boy of the same 

 weight. By approximately estimating the quantity of fat in the body 

 RUBNER was also able, from the protein condition, to compare the cal- 

 culated exchange of energy with that actually found. The exchange 

 per kilo amounted to 52 calories in the lean and 43.6 calories in the fat 

 boy, while, if the protein condition was a measure, one would expect 

 an exchange of calories of only 35 calories for the fat person. We cannot 



1 Cited from v. Noorden's Handbuch. 2. Aufl, page 97. 



3 Beitrage zur Ernahrung im Knabenalter, etc. Berlin, 1902. 



