New York AGRICULTURAL EXPERIMENT STATION. 41 
only evidence which these experiments supply along this line 
was obtained by the partial analysis of the milk fat from the 
cow which was the subject of the experiments detailed in Bul- 
Jetin 132. In this experiment the cow was fed a normal ration 
during a portion of the time she was under observation, so that 
it is possible to compare the fat produced before and after the 
food fat was almost entirely withdrawn. 
PARTIAL COMPOSITION OF MILK WITH NORMAL AND EXTRACTED Foops. 
f Reichert 
Periods represented AN oe number 
by different lots KIND OF RATION, cared 214 
of milk fat. eae mar grams 
™ OL fat. 
Wi Gy 
April 19 to 26.... Normal food. Food fat daily .63 Ib..... .96 16.3 
May 3tol10..... Extracted food. Food fat daily .125 1b.... .74 18.6 
May 10to17.... Extracted food. Food fat daily .125 1b.... .76 14.1 
May 17 to 24.... Extracted food. Food fat daily 125 lb.... .75 14.1 
May 24to31.... Extracted food. Food fat daily .125 1b.... .65 14.5 
May 3ltoJune? Extracted food. Food fat daily .125 lb.... .60 14.9 
June7tol4..... Extracted food. Food fat daily 125 1lb.... .60 14.9 
The Reichert number shows the relative proportion of volatile 
acids in milk fat. As an unmistakable and permanent drop 
occurred in this number immediately following the substitution 
of the fat-poor ration for the normal, it is fair to attribute to the 
food fat some influence upon the milk fat, though a single 
observation of this kind should not be taken as conclusive evi- 
dence. At the same time, the milk fat produced while the 
extracted foods were being fed contained a proportion of vola- 
tile acids larger than often found with normal rations. That 
the glycerides of these acids were formed in the cow and were 
not derived as such from the food is so evident as to render dis- 
cussion unnecessary. 
THE SOURCE OF MILK FAT. 
The main question involved in this investigation is the source 
of milk fat. The importance of the question and the reasons 
why it seemed to demand further investigation are set forth in 
Bulletin 132. It is sufficient to state in this connection that the 
inquiry is concerned with the relation of the several nutrients to 
