PHYSIOLOGY AND THE FOOD PROBLEM 21 



investigated is burnt inside the calorimeter and the rise 

 of temperature in the water is noted. Every substance 

 has a fixed heat (or energy) value. For example, a gramme 

 (about 15 grains) of starch or sugar when burnt yields 

 4 calories, and a gramme of fat yields 9, and this is true 

 whenever or wherever it is burnt. Life is a process of 

 slow combustion, and its activities are the result of the 

 transformation of energy just as in the furnace of the 

 steam-engine. In animal life, save in such exceptional 

 creatures as glow-worms and fireflies, there is no production 

 of light ; the chief form of actual energy is heat, and some 

 of this is transformable into mechanical work. Calori- 

 meters adapted to be used for animals and men have 

 shown that the same laws hold there as in the engine ; 

 each gramme of fat burnt in the furnace of our body 

 yields 9, and each gramme of starch or sugar (and we 

 may add here protein) yields 4 calories. The advantage 

 of fat as a fuel is evident, for it yields more than twice 

 as much energy as the same weight of any other food- 

 stuff. 



The daily calorie requirement will depend on the 

 size of the man and on variations in his activities. A man 

 of average size who stays in bed for the twenty-four hours 

 wants about 1700 in the day to maintain his temperature, 

 to keep his heart beating, his chest breathing, and so forth. 

 A larger man needs more, a smaller man less. The re- 

 mainder of his calorie supply in an active person can be 

 called upon for the performance of work. It should, 

 therefore, be one of our endeavours in hard times to get 

 rid of superfluous weight. This indeed is the usual effect 

 of reduced diet. The loss of weight is generally beneficial ; 

 it is not progressive after a given time, and one result is 

 a lessening of the figure 1700 (this is called the basal or 

 standard metabolic figure), so then more is available for 

 work performance. Most people happily do not spend 

 their days in bed, and the old precept that if a man does 



