CONDITIONS INFLUENCING METABOLISM 179 



efficacious in reducing than increasing the amount of adipose 

 tissue. 



Adipose Tissue a Reserve Supply of Energy. The carbohy- 

 drates and fats are preeminently the energy-producing foods, and 

 of these the carbohydrates, for reasons indicated, are the more 

 important. They not only furnish energy which is immediately 

 used up in running the machinery of the body, but they deposit, 

 or attempt to deposit, a reserve supply to protect the proteid por- 

 tions of the organism against accidents to temporary deprivation 

 of food, demands for an unusual amount of energy, malnutrition 

 from various causes, etc. sayings laid for the proverbial rainy 

 day. This reserve supply takes the form first of glycogen, which 

 is soon used up, meeting as it were only the demands of the hour, 

 and second of fat, which begins to be drawn upon when the glyco- 

 gen is exhausted, and which lasts for a length of time depending 

 upon its amount. 



Conditions Influencing Metabolism. Regular exercise is 

 undoubtedly favorable to the nutrition of any part, as e. g., the 

 muscles, the brain, etc. Exercise may mean increased disas- 

 similation, but if so it also means increased assimilation. With 

 regard to muscular exercise of average severity and reasonable 

 duration, the results of cellular activity seem at first a little sur- 

 prising, but are really to be expected if the concluding remarks 

 of the previous paragraph are true. The amount of urea under 

 such exercise is not appreciably increased which means that 

 disassimilation in the protoplasm of the muscle cells is not in- 

 creased. This remark holds good, however, only when the 

 supply of sugars, starches and fats is abundant; if they are not 

 present in sufficient quantity to meet the increased demand for 

 energy-supplying materials, then the proteids must be oxidized to 

 furnish it, and the urea discharged is increased. In striking con- 

 trast to the constant output of urea is the largely increased out- 

 put of CO 2 , representing oxidation of the carbohydrates and 

 fats. 



