LENGTH OF LIFE — APPLICATIONS 27 



pared the omnivorous averaged 1014 days, and the vegetarian 574 days, 

 or a ratio of 1,77 : i. If the average of all the omnivorous, including 

 both sexes, is compared with the average of all vegetarian rats we 

 have the relation of 1020 days to 555 days, or a ratio of 1.84 : i. 



Figure 19 shows in graphic form the total average lifetime of the 

 omnivorous rats (O) and of the vegetarians (V). The first group 

 lived almost twice as long as the last. This is a decided difference. 

 When we recall that all these animals were of the same age and as 

 nearly as possible the same parentage, were subjected to similar envir- 

 onment, and fed exactly the same food, with the exception that the 

 omnivorous group received animal food in addition about three times a 

 week, we must conclude that this great difference is due to the presence 

 of this animal food and to nothing else. 



GENERAL APPLICATIONS AND COMPARISONS. 



Any attempt to make a practical application of these results to 

 man, will no doubt be severely criticised by some on the ground that 

 what is true of the albino rat would not hold true in man, owing to the 

 wide difference in zoological position. Such a criticism would be based 

 on the prevalent idea that man is a supreme being, occupying a place 

 above animals, and with which he is not to be compared. 



The rat is by nature an omnivorous animal. All evidence points to 

 the fact that man is by nature an omnivorous animal. The character ot 

 the teeth and the digestive tract throughout are best adapted to a 

 mixed diet. His nearest related kin in the animal kingdom — the an- 

 thropoid apes — are all omnivorous feeders. In his savage state he par- 

 takes of the food most accessible, which includes animal food whenever 

 it is possible to secure it. There is probably no animal as capable of 

 adapting itself to so great changes in environment and in diet as man. 

 But though he is able to adapt himself to a restricted diet, is such a diet 

 capable of developing and maintaining his maximum mental and phy- 

 sical energy for a long period of life? It is not a question of what 

 food will keep the animal alive, but what diet will make it the most effi- 

 cient machine. It is not so much a problem of determining what foods 

 are necessary to maintain nitrogenous equilibrium in man, as it is of 

 ascertaining what diet is necessary not only to prolong mental and 

 physical efficiency during a long period of life, but to produce initiative 

 in these respects. 



The rats fed on the mixed diet had by far the greater initiative and 



