A Reversion of the Starch Dextrin Reaction. 117 



tration of the products of analysis, or by the addition of fresh 

 enzyme to a solution that had reached a state of equilibrium. In 

 the starch dextrin reversion the synthesis was attempted in an en- 

 tirely different and original way, that is, by a rapid increase of 

 temperature of a solution that is near or at the point of equilibrium 

 in relation to substances studied. In accordance with a known law 

 this change of temperature should move the point of equilibrium 

 endothcrmically. 



In studying this phenomenon it must be borne in mind that in 

 the digestion of liquid boiled starch there may be going on coinci- 

 dently at least three independently but serially related processes 

 which are dependent upon the activities of three enzymes — one, 

 in the depolymerization of the liquid starch into dextrins (amylase); 

 another, in the hydrolysis of dextrins into maltose (dextrinase); and 

 another, in the hydrolysis of maltose into glucose (glucase). Each 

 of these enzymes has its own optimal point of activity ; each car- 

 ries on its own reaction independently of the others ; and in each 

 reaction the substances entering into the reaction have their own 

 point of equilibrium of solution independently of the other reac- 

 tions. Hence it follows that each reaction, in so far as concerns the 

 reversion phenomenon in relation to the enzyme and the concentra- 

 tion of the solution and the temperature, must be studied separ- 

 ately. Conditions may be present that are favorable to the 

 reversion of one of the reactions but not of the others. 



In most of these experiments there was used 50 c.c. of a one 

 per cent, solution of boiled starch with 25 c.c. of a three per cent, 

 solution of Merck's "pure pancreatin." In a few experiments 

 ptyalin, malt diastase or Taka-diastase was substituted for pancre- 

 atin, and in some modifications were made in the concentration of 

 the enzyme. Digestion was usually carried on at room tempera- 

 ture, but sometimes at 37 0 C. The chief procedures and results 

 may be summarized as follows : 



1. If at any time after the reaction has proceeded so far that 

 the addition of a two per cent. Lugol's solution yields a violet reac- 

 tion (even though there be but the merest trace of coloration) the 

 preparation be heated quickly to the optimal point of saccharifica- 

 tion (approximately 6o° to 65°) the composition of the solution is 

 so altered that the addition of iodine now yields a blue reaction, 



