LIVING MATTER AND ITS PRODUCTS 155 



conditions a formation of isolactose from a solution containing 

 a mixture in equal concentration of its constituent hexoses, glucose, 

 and galactose; and even from glucose alone a disaccharide was 

 obtained. 



Similar evidence has been obtained of reversibility in the case 

 of certain esters of somewhat analogous constitution to the fats, 

 by the action of lipase, the fat- splitting enzyme of the pancreas; 

 from which by analogy the inference has been drawn that similar 

 syntheses of neutral fats by reversed enzymic action may occur 

 in the body. 



Thus, Kastle and Loevenhart digested a mixture of butyric 

 acid and ethyl alcohol with a fresh aqueous extract of pancreas, 

 and were able to detect ethyl butyrate by its odour, and, operating 

 on a large scale, were able to obtain a few drops of a light oil 

 with the odour and general properties of the ester. The changes 

 did not occur when boiled pancreatic extract was used, and since 

 in dilute solutions the same lipase can be used to convert ethyl 

 butyrate into butyric acid and ethyl alcohol, it becomes evident 

 that the action is a reversible one. In a later paper, Loevenhart 

 showed that a similar reaction was obtainable with a large number 

 of different tissue extracts. 



In a similar fashion, Hanriot showed that lipase is capable of 

 forming monobutyrin from butyric acid and glycerine. 



In so far, however, as the syntheses of simple esters by lipase 

 are considered to have a bearing upon the synthesis of neutral 

 fats by the same enzyme in the body, it must be pointed out that 

 the reactions are of somewhat different type, and that the equations 

 of equilibrium, taken in conjunction with the solubilities of the 

 neutral fats, show that the synthesis of neutral fats is a much more 

 difficult process, and one which, granted that it may occur by 

 reversed action of the enzyme under the conditions existing in 

 the cell, is exceedingly unlikely to occur in aqueous solution in the 

 test-tube. 



The difference arises from the fact that the two syntheses 

 achieved by the authors mentioned above of ethyl butyrate and 

 monobutyrin are produced in reactions in which single molecules 

 of each of the constituents unite to form a molecule of the ester; 

 while in the case of the neutral fats three molecules of the fatty acid 

 concerned unite with one molecule of the glycerine. If we represent 

 the osmotic pressures (which are proportional to the molecular con- 



