98 ORGANIC FUNCTIONING 



carbohydrates can be completely dried and then put into a bomb 

 calorimeter and burned in oxygen. In this way their available 

 energy, expressed as heat, can be found. 



One gram of protein so burned gives 4-0 calories 

 ,, carbohydrate „ ,, 4-0 



5? 55 I^t ,, ,, 0'9 5, 



(or figures very close to the above ones). 



Then the different kinds of raw and cooked foods are analysed 

 so as to give their percentages of dry protein, fat and carbo- 

 hydrate. From these analyses, and the above calorific values, 

 we can find the quantities of energy put into an animal, in the 

 form of its food. 



386. The Input and Output of Energy. Large calorimeters 

 are used in the experiments. The calorimeter is really a small 

 room, heat insulated and with perfectly controlled ventilation. 

 The quantities of air entering it are accurately measured and 

 the quantity of O2, CO 2 and OH 2 leaving it are also measured. 

 The excreta of the experimental animal are measured and 

 analysed. The animal is usually a medical student who works, 

 eats, excretes, sleeps, etc., for definite periods in the calorimeter. 

 The work done, say by riding an experimental, fixed bicycle is 

 recorded and so on. The animal, being in constant weight and 

 in " nitrogenous equilibrium," takes in so much energy in the 

 form of food, and gives out so much in the form of heat, mechanical 

 work, heat and calorific energy of the excretions and so on. 

 Thus an approximately accurate balance can be struck between 

 the input and output of energy. 



It has been found that the following quantities apply to the 

 average man. 



When sleeping he utilizes 1,500 calories per 24 hours, 



lying down ,, 1,700 „ ,, ,, 



sitting „ „ 2,400 ,, ,, „ ,, 



doing sedentary work ,, 2,400 

 doing heavy work ,, 4,000-6,000 

 and so on. The different experiments made give results that are 

 very much the same as those quoted above. 



If, in a great many experiments, the energy taken in is compared 

 with that given out the figures almost balance. Thus, for instance, 

 Energy input 418,665 Cal. Energy output 416,634 Cal. There- 

 fore the laws of conservation of energy and matter apply to the 



,, doing heavy work ,, 4,000-6,000 ,, ,, ,, 



