242 ELEMENTS OF PHYSIOLOGY 



orous : he ate tree fruit, both nuts and fleshy fruits. Tree 

 fruits contain all the four chemical classes of foods, pro- 

 teids, fats, carbohydrates, and minerals. The present 

 sources of his food, besides the original nuts and fruits, 

 are flesh, grains, herbs, and he has added them to his 

 dietary probably in the order named above. In the warm 

 regions of the earth, the banana, plantain, mango, orange, 

 and cocoanut trees bear their luscious fruit the year 

 round. But the multiplication of the race and perhaps 

 times of drought and famine led man to use the food 

 stored up in the flesh of other animals which had obtained 

 it from grass and herbs. This necessity doubly increased 

 with migration to colder climates. In the frigid zones 

 the inhabitants live very largely on animal food. They 

 consume immense quantities of blubber, or the fat of 

 certain animals, such as the whale, the walrus, and the 

 seal. This kind of diet, by sustaining the necessary bodily 

 heat, enables these people to withstand the intense cold to 

 which they are subjected. 



Grains in their natural state are too small and collect- 

 ing them was too tedious before the time of that long-for- 

 gotten genius who first thought of cultivating them in 

 order to improve them. Hunting is known to have pre- 

 ceded agriculture in all wild tribes. After flesh and 

 grains, last of all came vegetables. Fruits and grains 

 belong to the seed part of the plant. The coarser woody 

 leaves and stem and roots were probably not added to 

 man's food until the art of cooking was much advanced. 

 The degree of digestibility seems to coincide in most 

 persons with the order of adoption of the classes of foods 

 by the race. If one leads a sedentary life, or his digestion 

 becomes impaired, the weedy, fibrous vegetables should be 

 the first to be discarded from the diet, while flesh and 

 fruits seem to furnish the main substance for invalids even 

 after grains and starches prove hard to digest. 



