THE FOOD AND DIGESTION 



377 



just stated, the loss of heat per unit of weight is greater than 

 in their elders. Weight for weight, a child thus requires 

 a greater supply of energy than a man. The following 

 results, based upon observations on diets recorded by 

 Camerer, illustrate this : 



It will thus be seen that the energy requirements of chil- 

 dren at different ages may be stated in terms of the energy 

 requirements of an adult man doing average work. Atwater 

 formulates this as follows : 



Taking a man at 

 A woman 

 A boy of 14 to 16 

 A girl 



A child 10 to 13 



6 to 9 



2 to 5 



under 2 



. 1-0 



is equivalent to 0-8 of a man. 

 0-8 

 0-7 



0-6 

 0-5 

 0-4 

 0-3 



Mode of Life. An individual kept warm and at rest, re- 

 quires much less energy than if he is required to do muscular 

 work and is exposed to cold. The variations in the amount 

 of material used in different conditions is well illustrated by 

 the experiments of Zuntz on the excretion of carbon dioxide 

 in the dog. 



Resting lying 



standing .... 

 Forward movement (unloaded) 



(drawing weight) 



CO 2 excreted per 

 minute in corns. 



124-7 

 170-2 

 525-0 

 798-9 



These results are corroborated by a study of the diet re- 

 quired to maintain the weight and health of men doing 

 different amounts of work. From a large series of such 



