METABOLISM 195 



greatest rise in heat production. The effect in the case of pro- 

 teins is believed to be due to a stimulation of the cells of the 

 tissues to greater activity, the stimulation being produced by the 

 decomposition fragments of protein in the blood. In the case 

 of the carbohydrates and probably also of the fats, the effect is 

 believed to be due to the "mass action" of the fragments of 

 decomposition and not to a direct stimulating action. Since 

 proteins produce the greatest increase in heat production, they 

 should be eaten sparingly in hot weather. 



Curiously enough, increased mental activity does not increase 

 the heat produced by the body. This might be interpreted to 

 mean that mental activity uses -up no fuel, or an inappreciable 

 amount, but it is more nearly accurate to state that great mental 

 activity such as studying for an examination produces no more 

 heat than the mental activity of our ordinary and most indolent 

 mental processes. 



During sleep metabolism is low, but this is due probably to 

 lessened body activity rather than to any inherent differences 

 of metabolism. 



The variations of heat production in disease have been care- 

 fully studied by Benedict, Lusk, du Bois and others. In typhoid 

 and exopthalmic goitre there is a great increase. In diabetes 

 the increase is slight. 



Utilization of Alcohol by the Body. A problem of the great- 

 est importance has been to determine the position of alcohol in 

 metabolism. If burned in a calorimeter, alcohol yields over 7 

 calories per gram, and thus has a very high fuel value. A long 

 and careful study of the effects of alcohol on the body has been 

 undertaken by Benedict. In the body, small amounts of alcohol 

 undoubtedly are burned as fuel by the tissues. The effects of 

 alcohol are those of a depressant rather than of astimulant, 

 apparent stimulation being in reality a depression of inhibiting 

 influences. Although alcohol undoubtedly is burned as fuel by 

 the body, still it is a generally accepted fact that its poisonous 

 effect on the cells more than counterbalances any beneficial effect 

 resulting from its high fuel value. 



