32 CHEMICAL TRANSFORMATIONS 



found that in very concentrated solutions, the ferment of malt, 

 maltase, caused the formation of a disaccharide from glucose. 

 In his earlier work Croft Hill thought the disaccharide formed 

 was maltose, viz. the disaccharide on which the ferment naturally 

 works in the grain, and that the process was hence a direct reversal 

 of the action of the same ferment upon maltose in dilute solution. 

 Emmerling, who repeated the experiments, thought the disac- 

 charide formed in the concentrated solution of glucose was iso- 

 maltose. Then Croft Hill himself in later work found that the 

 substance formed was a new disaccharide which he termed 

 revertose. The important fact, however, remains that a ferment 

 which in dilute solutions of a disaccharide causes a hydrolysis into 

 hexoses or mono-saccharides ; in concentrated solution, acts upon 

 the hexose and causes a condensation to disaccharide. It was 

 further shown by Croft Hill that in dilute solutions, containing 

 less than 4 per cent, of glucose, the formation of the disaccharide 

 does not occur. 



It has since been shown by E. Fischer and E. F. Armstrong 

 that lactase, a ferment obtained from kefir, causes under like 

 conditions a formation of iso-lactose from a solution containing 

 a mixture in equal concentration of its constituent hexoses, 

 glucose, and galactose ; and even from glucose alone a disac- 

 charide 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. 



