70 TWENTY-FIFTH ANNIVERSARY REPORT. 
not fed to excess, were not detrimental to the production of 
milk nor to its quality for human consumption. It is true that 
in the early stage of the experiments the grains were fed injudi- 
ciously and exerted an ill effect upon the appetite of the cows. After 
the improper method of feeding was corrected, no difference could 
be observed in the milk as between the cows that were eating even 
putrid grains and those that were fed on the soundest kind of food. 
This should not be taken as an argument for feeding putrid material, 
because when the appetite of the animal and her general health are 
taken into consideration, there is always danger from such a food. 
It does mean, however, that many of the notions held by the public 
were not based upon accurately observed facts. A later test of wet 
starch waste, or slump, confirmed the conclusions of the first test, at 
least so far as acidity of food is concerned. This wet feed was fed 
after it had acquired 0.2 per ct. of free acid and during the same 
experiment hay and dry feed to which acetic acid had been added 
were given as one ration. The presence of this acid, either that 
from fermentation or that which was added, had no injurious effect 
whatever upon the health of the animals or upon the character of 
the milk. Indeed, the presence of a small amount of acid seemed 
favorable toward stimulating the appetite of the animals. 
THE FOOD SOURCES OF MILK FAT. 
One of the most elaborate and conclusive studies in animal nutri- 
tion that the Station has conducted was an investigation? into the 
food sources of milk fat... The popular notion had for along time 
prevailed that fat in the food was the source of the fat of milk. 
On the other hand it was held by certain scientific investigators that 
milk fat arises from the fatty degeneration of the proteid tissues of 
the udder. Previous investigations of this problem, including one 
made at the Station, had been inconclusive, because the rations fed 
were such that the fats present in the ration and the fat equivalent 
of the digestible protein of the ration were generally enough to ac- 
count for all fat in the milk. The plan of the Station experiment 
involved the extraction of practically all of the fat in the materials 
of the ration so that only the fat equivalent of the digestible protein 
was to be considered outside of the carbohydrates. Experiments 
with two cows demonstrated beyond any shadow of a doubt that the 
carbohydrates in the food must have served as raw material for the 

°Buls. 132 and 197; also in Rpts. 16:49-522 (1897) and 20:29-60 (1901). 
