170 BACTERIOLOGICAL AND ENZYME CHEMISTRY 



is known as the saponification of a fat. The term saponi- 

 fication has come to be a general one applied to all processes 

 whereby a fat is split up, yielding a fatty acid and glycerine ; 

 the process, indeed, is essentially one of hydrolysis and may 

 be expressed in general terms in the following equation, where 

 K = the residue of a fatty acid : 



R 3 C 3 H 5 + 3H 2 = 3RH + C 3 H 5 (OH) 3 



Such a reaction can, e.g., be brought about by heating a 

 fat with a mineral acid, or even by the action of steam under 

 pressure. 



Nature's method, however, for effecting this change, which 

 is of primary importance in the assimilation of fat by living 

 organisms, is as usual a much less drastic one. In the plant 

 or animal which uses fat to build up its body substances, 

 enzymes are produced known as lipolytic or fat-splitting en- 

 zymes, which are generally referred to as an individual enzyme 

 under the term lipase or steapsin. 



The decomposition of animal fats by lipase may be illus- 

 trated by taking butter fat as an example which is a compound 

 of glycerine and butyric acid. This is readily obtained by 

 melting a small quantity of butter in an evaporating dish 

 over a water-bath and pouring off the liquid portion, leaving 

 the solid residue of casein ; or more exactly by warming the 

 butter with ether, filtering through filter paper, and distilling 

 off the ether. The butter fat is a neutral yellow liquid, as 

 can be ascertained by testing the ethereal solution with 

 litmus paper. 



To determine the action of lipase upon it liquor pancreaticus 

 may be utilised. It was shown by Claude Bernard that 

 digestion of fat was mainly brought about by pancreatic juice. 



A few c.c. of butter fat may therefore be placed in a test- 

 tube and thoroughly shaken with a few drops of ' liquor 

 pancreaticus/ when an emulsion is formed. On warming 

 this emulsion on a water-bath or incubator at 40 C. for some 



