io6 



ELEMENTARY BIOLOGY 



COMPARATIVE LENGTH OF FOOD TUBE IN DIFFERENT GROUPS 

 OF MAMMALS 



This comparison proves very little, except that the relative length 

 of man's digestive tube is most like that of monkeys and pigs. It is 

 true that our food tube is three or four times as long as that of the 

 exclusive flesh-eaters, but it is about a third as long as that of the 

 exclusive vegetarians, like the cow and the camel. If the animals 

 nearest like man do indeed subsist upon an exclusively vegetarian 

 diet of fruit and vegetables, it may mean only that the monkeys have 

 neither the instincts nor the cleverness to provide themselves with 

 flesh food. The only important question to consider here is whether 

 in actual experience, or as a result of careful experiment, man can 

 thrive on a mixed diet. 



There are two really serious objections to the use of meat. 

 The first has to do with the chemical side. In the digestion 

 of meat there are produced substances that may be injurious 

 to the cells of the body. Some people can throw off these 

 poisonous substances more easily than others, and hence do 

 not suffer from them. Many people, however, accumulate these 

 products until they cause real injury. Moreover, it has been 

 found that bacteria thrive better in the intestines of flesh-eaters 

 than in the intestines of non-flesh-eaters, and the products 

 of the activity of these bacteria may be injurious to many 

 people. Finally, with the use of meat we are more likely to 

 get an excess of protein than we are with the use of exclu- 

 sively vegetable food. This is a real danger, because any excess 



