The seasonal differences in the growth of the rats l > 2 > 42 and 

 the possible seasonal variation in the vitamin content of the 

 milk 1 2 > 41> 42 > 43 > 44 are eliminated here, since the experiments 

 (Tables V and VI) were carried on at the same time in the 

 early spring, late winter milk from the same lot being used in 

 both series. The four rats receiving 7 cc. of reconstructed 

 milk which had been heated, died at the ages of 50, 60, 66 and 

 66 days respectively, while the rats getting the same amount 

 of unheated milk lived till the end of the twelfth week when 

 they were killed. This is additional evidence of the destruc- 

 tion of vitamin B by this heat treatment. 



Dry heat applied for 6, 24 and 48 hours seems to have 

 little or no deleterious effect, as the weight curves of the 

 control rats receiving unheated milk and of those receiving 

 the heated milk are approximately the same. 



Experiments with Milk Mixed with the Rest of the Diet. 

 Preliminary experiments reported elsewhere in this paper in- 

 dicate that a change in the vitamin B content of skimmed milk 

 powder may be most easily observed if the milk is mixed with 

 the rest of the diet in the proportion equal to 25 per cent, of 

 the entire mixture. Therefore the unheated milk of Diet 100 

 was replaced by the milk heated dry for various periods, 6, 24 

 and 48 hours. The animals from .mothers on Diet 13 M and 

 Diet 13 placed on these diets have been summarized separate- 

 ly in Tables XV and XVI and the combined results are given 

 in Table XVII and Chart II, Figure II. It will be noted here 

 again, as was observed from the results of the experiments in 

 which different amounts of milk replaced the starch in Diet 

 94 (Tables IX and X) that the rate of growth of the animals 

 from Diet 13 M is greater than that of the animals from 

 Diet 13. 



The total food consumed by the animals on Diet 100 and 

 the diets in which the unheated milk of this ration was re- 

 placed by the milk heated 6, 24 and 48 hours was practically 

 the same in each case. The rats therefore received essentially 

 the same number of calories and equal amounts of protein, of 

 the mineral elements and of the vitamin containing food on 

 the four different diets. 



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