n8 HUMAN PHYSIOLOGY 



weight is considered, it will be found that children need a 

 larger amount than adults. This is due to two causes: 

 first, a growing body needs relatively more food than an 

 adult, and secondly, the metabolism of children is relatively 

 greater than that of adults because of the greater proportion 

 of surface (thereby greater loss of heat) compared to the 

 heat producing mass (see Chapter XIII). 



For one kilogram of body weight the following amounts 

 are necessary: 



X 



Age. Proteid. Fat. Carbohydrates. 



2-6 years , . . 3.7 g 3.0 g 10.0 g 



7-15 years 2.8 g 1.5 g 9.0 g 



Adult 1.6 g 0.8 g 8.0 g 



Besides the foodstuffs we still take up many substances 

 which are not necessary for the maintenance of the body, 

 but which are, nevertheless, of physiological importance. 

 They are the condiments. They include substances having 

 a specific taste and odor which stimulate the nervous system, 

 increase digestion, aid circulation, etc. Under this class 

 we may mention spices and certain alkaloids (caffein in tea 

 and coffee, theobromin in cocoa, nicotin in tobacco). 



There are still other organic substances (e.g. vegetable 

 acid, many alcohols) which are also burned in the body and 

 can therefore be regarded as energy-yielding foodstuffs even 

 though they are not necessary for the body. As far as ethyl 

 alcohol is concerned, its worth as a food is doubtful since it 

 acts as a violent poison and its frequent use produces morbid 

 changes in almost all the organs of the body. 



2. FOODS 



The foods furnished us by nature are mixtures of the food- 

 stuffs. They may be classified as : 



1. Food from the animal world. 



2. Food from the vegetable world. 



The composition of the chief foods is as follows : 



