SUMMARY AND CONCLUSIONS. 163 



in other words, that through the evolution of this basic property there have been brought 

 about, and there is being brought about continually in all li\'ing matter, those various 

 modifications of responsivity or irritability which we can readily observe if not explain. 



(5) That there is no justification for the assumption of the existence of amylodextrin and 

 maltodcxtrinas indi\-idual substances which have properties intermediate between starch and 

 dextrin, and dextrin and maltose, respectively. It seems to ha\^e been shown quite clearly 

 that they are merely mixtures of variable composition depending upon the particular kinds 

 of substances entering into them. For reasons that are perfectly obvious the use of the 

 words amylodextrin and maltodextrin should be discontinued, and especially the former, 

 because of its indiscriminate use in designating soluble starch, special forms of starch, mix- 

 tures of starch and dextrins, etc. Likewise a clearer understanding of the dextrinous products 

 of starch will be had by dropping multiple names for dextrins (nearly all or all of which are 

 names for impure substances and unknown mixtures) and using exclusively erythrodextrin 

 and achroodextrin, until at least these latter bodies have been satisfactorily studied. 



(6) That under various modifications of experiment abnormal forms of dextrin, and 

 also gums, and also unusual saccharine products, etc., may be formed and that the proc- 

 esses may be carried beyond the sugar stage by the presence of certain enzymes, bacteria, etc. 



(7) That the products of decomposition by high and dry heat, and by dilute acids and 

 enzymes, and different acids, and different enzymes are not in all respects identical. The 

 dextrins formed by torrefaction, acid action, and enzymic action are not absolutely identi- 

 cal, and especially interesting is the comparison of the products of acid and enzyinic action 

 with each other, and of these with those of torrefaction. In fact, it seems probable, had 

 we adequate methods for differentiating the vast number of hypothetical stereoisomeric 

 forms of starches and of dextrins, that it would be found that corresponding dextrins, 

 as for instance some specific kind of erythrodextrin that is produced by mineral acid, 

 organic acid, enzyme, or heat, would exhibit such differences as to show that we have as 

 many stereoisomeric forms as we have types of means of producing them. In fact, one 

 might go further and hold that the product of the plant enzyme will differ from that 

 of the animal enzyme, and that as plant and animal enzymes differ in essential respects 

 from one another, the product will be correspondingly modified. The conception held by 

 many that dilute acids and enzymes merely increase the velocity of reactions seems dis- 

 proved by the fact that the products of the reactions of these two classes of decomposing 

 agents differ not merely quantitati^ely but also qualitatively. It seems obvious, if the 

 effects were merely those of an energizer, that no qualitative differences such as have been 

 reported would be noted in the digestions by acids and enzymes. That they increase the 

 velocity of reactions must be admitted, and likewise that any substance under appropriate 

 conditions may act catalytically, but there are certain special properties which are attached 

 to each catalytic body and its modes of action which must not be ignored. 



(8) Accepting the hypothesis of van't Hoff that an enzyme gives rise only to such 

 products in the analysis of a given substance as it will under appropriate conditions com- 

 bine in the synthesis of the same substance, and coupling this hypothesis with the concep- 

 tion that the synthesis of starch in the plant is essentially fundamentally through the 

 actions of enzymes, it is obvious that accurate knowledge of the processes in plants during 

 this synthesis, and accurate knowledge of the processes in the analysis by the same enzymes 

 in vitro, would be mutually helpful and corrective, the one checking the other. Hence 

 the importance of comparative investigations and of advances in one investigation fore- 

 telUng identical advances in the other. Thus, if in vitro by the agency of plant enzymes 

 sugar may be reduced to aldehyde and this to CO2, and H2O, we may with confidence look 

 for the reverse processes in the plant, which is essentially synthetic in contradiction to 

 enzymic processes in vitro which are under the usual conditions of experiment essentially 

 analytic; but the latter we may have reversed under appropriately altered conditions. 



