IGO DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



of plants and plant-parts justifies the asraimption of Meyer (page 51) that in accordance 

 with these differences we ha^e different biologic mechanisms. Hence it would seem to 

 follow, for reasons stated on page 11, that corresponding metabolites should be modified 

 in accordance with the modifications of the mechanisms which produce them. In the second 

 place, it has been shown that saccharose, or cane sugar, can be obtained from starch as one 

 of the products, and that the plant may utilize saccharose in the synthesis of starch. This 

 holds good for maltose and other sugars which have a very difTerent chemical constitution 

 from saccharose. If, therefore, sugars differing so in chemical constitution are used in the 

 synthesis of starch, it seems probable that such constitutional differences tend to be carried 

 throughout the whole series of sj^ithetic bodies and to be present ultimately in the starch 

 or glycogen molecule. One can readily conceive how, through the operations of these two 

 factors (differences in the Itting viechanism and differences in the building material), each 

 species of plant, or even each individual, may produce a specific kind of starch; and, more- 

 over, that this product may be modifiable under normal or abnormal conditions, owing 

 to temporary or permanent modifications of the plastids, or of the food supply, etc. An 

 instance of such a modification is found in the pecuhar form of glycogen found by Claude 

 Bernard in paralyzed muscles the glycogen of normal muscles yields a reddish or port- 

 wine color reaction with iodine, while the abnormal glycogen yielded a blue reaction. 

 Even after a given form of starch is produced it may undergo a spontaneous change into 

 another stereoisomeric form (see page 9). 



SUMMARY AND CONCLUSIONS. 



One can not review the literature of the decomposition products of starches without 

 a realization that our knowledge is exceedingly inexact and that we have scarcely reached 

 the tkreshold of accurate information of the characteristics of the various homologous 

 forms of starch, of the actual substances that are formed as intermediate products during 

 the process of saccharification, and of the precise chemical processes involved in the several 

 reactions. The available methods for the differentiation of homologous forms of starch 

 have been used to but a very limited extent and (as in case of the differentiation of simi- 

 larly related bodies) they are for the most part crude and almost wholly quantitative. 

 The methods of measurement of the progress of the ^^arious steps in the saccharification 

 of starch and the methods of separation of the intermediate bodies and the results of their 

 study are quite as unsatisfactory. Exactly when any one stage begins and ends, when the 

 last molecule of starch disappears and when the first molecule of achroodextrin appears, 

 whether or not there exists any form of dextrin that will reduce copjier solutions or which 

 through some obscure relationship with maltose will affect its reactions with copper, 

 and whether there are multiple forms of erythrodextrin and of achroodextrin, are but a 

 few of the fundamental questions that requu-e the final answer. 



In a word, the determination of the sequence of events and their relations and the exact 

 products formed remains to be demonstrated, for as yet the only means we have of ascer- 

 taining the degree of progress of enzymic saccharification that has even an approach 

 to accuracy is the estunation of the amount of maltose, as for instance by the copper 

 test, which is the best; but this may be attended by more or less fallacy because of the 

 existence of an achroodextrin or other non-saccharine body which may take part in the 

 reaction, or because of the presence of variable amounts of glucose which has a very difTer- 

 ent reducing value, in addition to other distinctive properties. Finally, the assumption 

 that the processes are those of successive hydrolysis does not take into account the fact 

 that the liquefaction of raw starch or starch-paste is doubtless not one of hydrolj^sis but of 

 adsorption; or that the conversion of starch into dextrin, and of a higher form of dextrin 

 into a lower form, is in effect a depolymerization ; or that oxygen may be essential during 

 a part of or throughout the entire group of reactions. 



