The seasonal differences in the growth of the rats! ® * and 
the possible seasonal variation in the vitamin content of the 
milk +» 2» 44, 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 13M 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 13M 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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