84 



THE FEEDING OF ANIMALS 



115. Fatty acids. Free, fatty acids exist in nature. 

 They are not found in butter, lard, and tallow unless 

 these substances have undergone fermentations and 

 become rancid. The characteristic flavor of strong butter 

 is due to free butyric acid, which, because of fermenta- 

 tions, has parted from the glycerin with which it was 

 originally combined in the milk. In plant oils, on the 

 other hand, are found considerable proportions of the 

 free fatty acids, some of which have not been discovered 

 so far in animal fats, either free or uncombined. 



116. Ether-extracts. Stellwaag investigated the in- 

 gredients of the ether- and benzine-extracts from plants. 

 His results show that not only do these extracts include 

 substances which are not fats, but that a considerable 

 proportion of free, fatty acids is always present, sometimes 

 in quantities exceeding the neutral fats: 



TABLE XXIV. COMPOSITION OF ETHER-EXTRACTS 



It appears, as before stated, that ether-extract, espe- 

 cially that from vegetables, may consist, to some extent, of 

 materials which should not be classed among the fats. 

 The extracts from the grains proved to be nearly all oil. 

 Moreover, the grain oils were made up principally of gly- 

 cerides, and those from potatoes and beets consisted 

 largely of free, fatty acids. 



