68 SELECTION AND PREPARATION OF FOODS 



combines the two, have some teeth adapted for one kind 

 of food and some for the other. 



Of stomach and intestines. --The stomach and intes- 

 tines of animals are also adapted to their diet. The 

 uncooked flesh of animals is the most easily digested of 

 foods and therefore carnivorous animals have a simple 

 stomach and short intestines. Plant tissues, on the con- 

 trary, are very difficult of digestion and in consequence 

 the majority of herbivorous animals have a large and 

 complicated stomach and very long intestines. Animals 

 living upon both a flesh and a vegetable diet have a 

 stomach and intestines the size and structure of which 

 lie between these two extremes. The same is true of 

 animals like squirrels which, although herbivorous, live 

 upon the more easily digested forms of plant substances, 

 as fruits. 1 



Diet of man. As man is the most widely distributed 

 animal upon the earth's surface, the different races of 

 men have been for many thousands of years exposed to 

 very different conditions of climate and food supply. 

 The diet of man is therefore as varied as are the con- 

 ditions under which he lives. In the frozen north, his 

 diet is principally fatty animal food; in the equatorial 

 regions, it is largely vegetable; whereas in the tem- 

 perate regions, it ordinarily combines both. 



Relation of food to muscular energy. In spite of 

 these variations in the kinds of food eaten, it has never- 

 theless been found that in general the amount and funda- 

 mental character of the food required by men depend 

 upon the amount of work which they do. The doing 

 of work depends upon the development of energy. This 

 in turn means that the food eaten must be combined 



1 Technically, fruits include all seeds of plants with their closely 

 related structures, as nuts, grains, pumpkins and apples. 



