30 THE PROTEIN ELEMENT IN NUTRITION 



products of the uncultivated vegetable kingdom. In the later 

 period the period of stationary agriculture when there was 

 an abundance of animal and vegetable food materials, and when 

 a large part of the total sum of human energy was liberated and 

 made available for other purposes than the quest of food, a 

 physiological division of labour was made possible, and social 

 progress made headway. 



The general effects of agriculture upon man's diet have been 

 to accelerate the previous abandonment of raw vegetable food, 

 and to increase the amount of starchy foods. The concentration 

 of the diet, epoch by epoch, has become more and more marked, 

 so that at the present time it forms the outstanding feature of 

 the food of mankind. Another result of the development of 

 agriculture and the cultivation of fruits, such as the date, the fig, 

 the grape, and the banana, is the rapid increase in the quantity 

 of sugar entering into man's diet. 



The conclusions Dr. Campbell arrives at from his researches on 

 the dietary of evolving man are 



1. The fact that man has evolved from the ape on a highly 

 carnivorous diet disposes of the contention that man is essentially 

 vegetarian by nature, and that meat and other animal foods are 

 harmful. 



2. The fact that up to the beginning of the agricultural period 

 man's supply of sugar was scanty, whereas during it, and especially 

 within recent times, it has been enormously increased, suggests 

 that ill-health may often result from its excessive use. As a 

 matter of experience in the dieting of patients, more good can be 

 done by curtailing the starchy foods and sugar than by cutting 

 down animal food, and this even in such diseases as gout and 

 megrim. 



3. So far as the general results affect the food of mankind, 

 the ideal dietary is one that is simple in quality and moderate in 

 quantity. It should contain a fair proportion, a quarter to one- 

 third, of animal food. A certain amount of vegetable food 

 should be uncooked in order to compel thorough mastication, 

 and excess of sugar should be guarded against. 



The general bearing of Dr. Campbell's work on the foodstuffs 

 and diet of evolving man would be to show how very important 

 a part has been played by the protein element. The food of 

 existing precibiculturists is estimated as being composed of half 

 animal and half vegetable material, so that the degree of nitrog- 

 enous interchange within the body should reach a high level. 



