20 EFFECT OF DIET ON THE ALBINO RAT 



We thus have the same amount of work done by the two classes. 

 The vegetarians required 19.8 months, or the whole of their lifetime, 

 while the omnivorous needed only 20.9% of their lifetime, and aver- 

 aged 6.2 months of age. Thus the ratio of omnivorous to the vegeta- 

 rians in regard to efficiency would be 100 : 20.9, or about 5 : i. We 

 must not lose sight of the fact that this difference in ability to do work 

 is caused by the presence of animal food in one diet and the absence of 

 it in the other, this being the only difference in the environment. 



If a table were made comparing the amount of work done by each 

 class at the same average age, the difference would be more marked 

 than just shown. It is not considered necessary to construct such a 

 table. 



GROWTH. 



We have just considered what a marked effect on the efficiency of 

 the rat these two diets had. Let us now consider the effect on growth. 



The rats were weighed before feeding about once each two weeks. 

 Weighings made approximately a month apart were selected in making 

 Table VIII. This shows the individual weights of each of the sixteen 

 rats at intervals of about a month during their entire lifetime. The 

 young at the age of thirty days thus appear to be nearly uniform in 

 size. The advantage is slightly in favor of the vegetarians, the males 

 averaging 42 grams and the females 39 grams, while the omnivorous 

 male averaged 41 grams and the female 38 grams. Twenty-eight days 

 later, when the two groups were put on the omnivorous and vegetable 

 diets, the sexes averaged approximately the same. Eleven days later a 

 difference in the rate of growth is already noticed. This is more 

 obvious in Table IX, which represents the averages of each sex in the 

 different groups. As the rats became older this difference in weight 

 was more and more noticeable, becoming greater as age advanced. 



It was previously noted^ that the control rats surpassed the exer- 

 cised ones in weight. The same is observed here in both groups of 

 rats. This is especially noticeable in the curves of Figure 13, which 

 represent the data of Table IX. The heavy lines are the averages of 

 the omnivorous rats, the light lines the vegetarians. The male in each 

 case is decidedly heavier than the female of the same group. Also the 

 control and exercised males excel both the control and exercised fe- 

 males of the omnivorous group. This relation does not exist in the 

 vegetarian. The heaviest omnivorous female exceeds the heaviest vege- 

 tarian male by 9 grams and the heaviest vegetarian female by 36 grams. 

 The maximum weight in each of these tables is shown in bold type. 



