ON THE METHOD OF METABOLISM EXPERIMENTS 



91 



We have already seen that under normal circumstances no nitrogen is 

 eliminated in the expired air as a product of metabolism, and that in the 

 sweat only in exceptional cases is the quantity of any importance. Hence 

 the channels by which nitrogen is excreted are the kidneys and the intestine 

 as will appear plainly from a case of nitrogenous equilibrium. 



If an animal be given a diet, which from day to day contains exactly the 

 same quantity of nitrogen and does not vary with regard to the nonnitrogenous 

 foodstuffs, after a few days one finds in the urine and faeces exactly as much 

 nitrogen (and sulphur) as had been ingested in the food. This condition is 

 called nitrogenous equilibrium. As an example the following experiment from 

 Gruber may be given: 



D. EXAMPLE OF A METABOLISM EXPERIMENT 



The following table after Atwater contains a summary of the ingesta and 

 excreta in an experiment with mixed food. The experiment lasted four days, 

 the subject being a man thirty-two years of age and of about 64 kg. body 

 weight, who remained as quiet as possible throughout the experiment. 



Ingesta, mean iveight in g. per day 



Excreta, mean weight in g. per day 



