Isnw York Agfjcultural Experiment Station. 



41 



only evidence whicli these experiments supply along this line 

 was obtained by the partial analysis of the milk fat from the 

 cow which w^as the subject of the experiments detailed in Bul- 

 letin 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 food fat was almost entirely withdrawn.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 ^vitii Normal and Extracted Foods. 



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 glvcerides 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 fo'^th in 

 Bulletin 132. It is sufficient to state in this connection that the 

 inquiry is concerned with the relation of the several nutrients to 



