82 THE FEEDING OF ANIMALS 



foods and in the arts. In many cases, the refuse from this 

 extraction goes back' to the farm as food for cattle. This 

 is especially true of linseed and cottonseed. 



112. Nature and kinds of fats. — ^The vegetable and 

 animal fats and oils may, for convenience' sake, be dis- 

 cussed in two divisions, the neutral fats, or glycerides, and 

 the fatty acids. The neutral fats are combinations of the 

 fatty acids TOth glycerin. When, for instance, lard is 

 treated at a high temperature with the alkalies, potash 

 and soda, glycerin is set free, and an alkali takes its place 

 in a union with the fatty acids. This is the chemical 

 change which occurs in soap-making. There are several 

 of these neutral fats, the ones most prominent and impor- 

 tant in agriculture being those abundant in butter and 

 in the body fats of animals, viz., butyrin, caproin, cap- 

 rylin, caprin, laurin, myristin, olein, palmatin, and 

 stearin, the last three being the most abundant and impor- 

 tant in human foods. Butyrin is a combination of buty- 

 ric acid and glycerin, stearin of stearic acid and glycerin, 

 and so on. Because these are combinations of three 

 molecules of a fatty acid radical with one of glycerin, 

 they are sometimes named tri-stearin, tri-palmatin, and 

 tri-olein, and so on. Some single fats (glycerides) are 

 compounds of two or three fatty acid radicals united with 

 gly6erin in the same molecule. As glycerin is an alcohol, 

 and as combinations of an alcohol and acids are ethers, 

 the neutral fats are really ethers (esters), although they 

 differ greatly from the common conception of an ether 

 which is gained from ethyl ether or the ether of drug-stores. 



113. Physical properties of the fats and oils. — ^These 

 individual fats possess greatly unlike physical properties. 

 They are all soluble in benzine, chloroform, and ether, 

 and insoluble in water. At the ordinary temperature of 



