METABOLISM. 499 



Basal Requirements. 



The basal energy exchange is inversely proportional to the weight 

 of the body and directly proportional to the body surface. The con- 

 dition of the body also has an influence on the basal requirement. Any 

 special consumption of either fat or carbohydrate in the body 

 metabolism is indicated at once by a corresponding change in the 

 respiratory quotient. 



The Energy Requirement of an Adult. 



The minimal requirement, according to Atwater, for a man at rest 

 is 2,241 calories. Hence a ration which does not supply 2,000 calories 

 net must be inadequate for a laborer, for a waste of 10 per cent, must 

 be deducted from the calculation in determining the net requirement. 



In an atmosphere of a temperature of from 30 to 35 degrees C. 

 the minimal requirement for energy is seen. The effect of temperature 

 -on metabolism is not due, according to Voit, to rigors or to increased 

 respiratory muscular activity. He believes it to be the reflex stimulus 

 of cold on the skin which raises the metabolic activity of the muscles. 



The amido-acids resulting from the breaking up of proteids are 

 equivalent in metabolism to the ingested proteid itself. 



As regards the effect of temperature on metabolism, Rubner gives 

 two laws, which have been summarized by Lusk: 



First. The first law is that within limits normally compatible 

 with life, warm-blooded animals are capable of adapting themselves to 

 change in external temperature through a reflex increase or decrease 

 of activity of their heat-producing apparatus. For every state of 

 body substance and for every temperature of the environment there 

 is a definite amount- of heat-loss to which the organism, with the aid 

 of its heat-regulating apparatus, tends to approach. 



Second. The second law is that physical regulation can never 

 enter as a factor unless the conditions of the first law are fully 

 satisfied; that is, until the heat-production equals the requirement 

 of the organism. If, however, the heat-production be greater than 

 corresponds to the minimal requirement for that temperature, then the 

 heat-production within certain limits remains independent of the 

 temperature. Under these circumstances the heat-production does not 

 decrease on raising the external temperature, and only increases when, 

 through increasing cold, the former heat-production no longer covers 

 the minimal requirement of the organism for heat. 



The second law explains why in certain cases after food ingestion 

 the carbon dioxide excretion may remain constant with changing 





