172 BACTEEIOLOGICAL AND ENZYME CHEMISTRY 



with the ground seeds for twenty-four hours. The solution is 

 then filtered and can be tested for the presence of lipase. 



To test for the presence of lipase, either in the ether extracted 

 residue of the seeds, or in the solution obtained as described, 

 an emulsion of castor oil is made by thoroughly shaking, 

 say, 5 c.c. of the oil with a little gum arable. Six test-tubes 

 may now be made up as follows : to each of them 2 c.c. of a 

 castor oil emulsion may be added together with a drop or two 

 of neutral litmus, to two a few centigrams of the residue 

 from the ether extraction of the seeds may be added, to two 

 others, say, one c.c. of the sodium chloride extract, while the 

 remaining two test-tubes are left as controls. One test-tube 

 from each pair is now boiled, and after cooling all six test-tubes 

 are incubated for some hours at a temperature of 35° C. In 

 the case of the tubes containing the unboiled enzyme the 

 formation of acid will be evident from the reddening of the 

 litmus, while the boiled liquids, and the unboiled hquid to 

 which no enzyme has been added, remain unchanged. 



The actual amount of acid produced can be determined 

 by adding dilute standard caustic soda, say j^, till the blue 

 colour of the litmus is restored. 



Not only is lipase capable of splitting up fats properly 

 so-called, but it can also decompose simpler esters, and the 

 reaction in such a case, owing to the more complete solu- 

 bility of the products, is capable of being more exactly studied. 

 For this purpose ethyl butyrate, which has the formula 

 CgHjCOgCgH^, has been utiUsed by several investigators. 

 Among these researches those of Armstrong and Ormerod in 

 England and Kastel and Loevenhart in America may be 

 specially mentioned. Armstrong and Ormerod made use of the 

 dried residue obtained on extracting the castor oil with ether ; 

 they found that the action of the lipase was increased by the 

 presence of dilute acid. Their investigations were directed 

 towards finding some chemical explanation of the action of 

 the enzyme, and for this purpose they investigated a number 



