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PHYSIOLOGY 



quantity of different articles of food, perhaps especially of those rich in 

 protein, than in a limitation to foods obtained from the animal or vegetable 

 kingdom. In certain individuals the increased bulk of indigestible residue 

 which is afforded on a vegetarian diet presents a distinct advantage, since 

 it serves to promote peristalsis and the normal evacuation of the large 

 bowel. There is no scientific evidence that for the ordinary person any 

 advantage is to be gained by adherence to a strictly vegetarian diet. 



THE DIET OF THE GROWING ANIMAL 



Since the young animal is smaller than the adult, it presents a greater 

 surface in proportion to its bulk, and therefore will need more energy per 

 kilo body weight than is the case with the adult. The processes of growth 

 are attended moreover with an active metabolism, so that the metabolism 

 is more energetic in the young animal than in the adult, even if we take into 

 account the relative surface in the two cases. In the following Table is 

 given a number of observations showing the output of carbon dioxide per 

 square metre body surface at different ages in boys and men : 



EFFECT OF AGE ON METABOLISM (MAN) 



Between the ages of fourteen and nineteen years in boys the carbon 

 dioxide output is absolutely greater than at any other age. It is during these 

 years that the growth of the boy is most marked. A boy between nine and 

 thirteen years old requires just as much food as a full-grown man, and 

 between the ages of fourteen and nineteen he will require more. This great 

 increase between the fourteenth and nineteenth years is not noticed in 

 females. There is a gradual absolute increase in girls up to the eleventh 

 year. At this age and henceforward the total carbon dioxide output and 

 therefore the total food requirements remain constant, being about equal to 

 that of a woman of thirty. The total energy requirements of the growing 

 animal are not, however, the only factor which we have to consider. The 

 protein of the food has not only to replace the wear and tear of tissue, but also 

 to provide material for the growth of new tissues. The protein needs there- 

 fore of the growing animal are relatively greater than those of the adult, and 

 absolutely greater during the period of most rapid growth, namely, in boys 

 between the ages of fourteen and nineteen. It is a popular belief that in 

 a working-class family the worker or wage-earner needs a greater protein 

 supply than the rest of the family. This is a mistake. The adult worker 

 can obtain his energy equally well from carbohydrates and fats, whereas 



