152 PHYSIOLOGY OF ALIMENTATION. 



1000 c.c. of an extract of ground pancreas were mixed with 

 1900 c.c. of a 1/10 normal butyric-acid solution and 100 c.c. 

 of 95 percent alcohol. To the mixture was added some 

 thymol to prevent the development of bacteria, and the 

 whole was kept for 40 hours at a temperature of 23 to 27 C. 

 A similar mixture was prepared as a control, only the pan- 

 creatic extract was boiled before being mixed with the 

 butyric acid and alcohol. At the conclusion of the experi- 

 ment 25 c.c. were distilled over from each of the flasks. 

 Had any etjiyl butyrate been synthesized from the butyric 

 acid and alcohol this distillate ought to contain it. It was 

 found that the distillate from the first flask, containing the 

 unboiled pancreatic extract, smelled strongly of ethyl butyrate, 

 and after being further purified rendered water milky when 

 poured into it, owing to the formation of the only partially 

 soluble ethyl butyrate droplets; it formed a soap (sodium 

 butyrate) upon the addition of NaOH, and yielded butyric 

 acid when digested with lipase. The distillate from the flask 

 containing the boiled pancreatic extract smelled of bmtyric 

 acid, gave no turbidity when poured into water, and was un- 

 changed through the addition of lipase. A synthesis of 

 ethyl butyrate from butyric acid and alcohol under the in- 

 fluence of a substance contained in the pancreas and de- 

 stroyed by heating in other words, the synthesis of an 

 ester under the influence of lipase seems proved by this 

 experiment. 



Just as in the analysis of an ester (or fat) the reaction is 

 incomplete, so, too, is the synthesis. Before all the butyric 

 acid and alcohol have been built up into ethyl butyrate, the 

 reaction comes to a standstill (practically speaking). We 

 are in this case also dealing with a reversible reaction cata- 

 lyzed by a ferment. The lipase acts just as the maltase did 

 in the case of maltose and glucose it only hastens the estab- 

 lishment of an equilibrium between the fat (ethyl butyrate 

 in this case), on the one hand, and fatty acid and alcohol, on 

 the other. Whether lipase will have an analytic or a syn- 



