84 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



etc. That the starches of different plants are not chemically identical is not only suggested 

 by the marked differences in histological peculiarities, polariscopic properties, behavior 

 to heat, reactions with stains and with various reagents, etc., but also by the differences 

 in the conditions, protoplasmic and otherwise, under which the starch is formed. 



The literature bearing upon the subject of the primary decomposition products 

 contains many inconsistencies, contradictions, errors of observation and deduction, and 

 baseless conclusions, and we are as yet very far from being satisfactorily informed as to 

 the exact processes involved, or the exact products formed, or of the various conditions 

 under which the products may be modified. The earliest literature of the products of the 

 decomposition of starch, up to 1836, was reviewed by Poggendorff (Ann. d. Physik u. 

 Chemie, 1836, xxxvii, 115). Subsequent publications, up to 1874, were very briefly 

 abstracted by W. Niigeli (Beitrage zur naheren Kenntnis der Starkegruppe in chemischcr 

 und physiologischer Bezeihung, Leipzig, 1874, 106). Since this time a voluminous literature 

 has accumulated. In 1872 a new era in these investigations was initiated by the discovery 

 of Griessmayer and Briicke, working independently, of the formation of two kinds of dextrin, 

 one giving a red reaction with iodine {erythrodextrin) but the other no coloration (achroodex- 

 trin); and by the rediscovery by O'Sullivan of the sugar described by Dubnmfaut in 1823, 

 and named by O'Sullivan maltose. 



SYNOPSIS OF THE MORE IMPORTANT LITERATURE UP TO THE INVESTIGATIONS OF 

 GRIESSMAYER, BRUCKE, AND O'SULLIVAN IN 1872. 



The observation of Leeuwenhoek in 1716, that the starch-grain consists of a non- 

 nutritive outer coat or integument and an inner nutritive substance, seems to have been 

 the earliest step in the study of the structural units and derivatives of starch, which body, 

 as Poggendorff pointed out in 1836, was up to that time one of the most studied and least 

 understood of all substances. Poggendorff's statement was virtually repeated, ten years 

 later, by Schleiden (Principles of Botany, 1849), and twenty years later by von Mohl 

 (Botanische Zeitung, 1859, xvii, 225), the latter writing that more microscopical researches 

 with starch-grains have been made, and in the course of time a greater number of contra- 

 dictory teachings concerning the structure and chemical composition of starch-grains have 

 been uttered than of any other plant structure. In fact, von Mohl's statement might 

 with justification have been writ^ten at the present day. 



Our knowledge of the primary decomposition products had its origin in the discovery 

 of Vaquelin (Bull. d. pharm., 1811, in, 54) that by torrefaction starch is converted into a 

 gummy substance (Starkemehlgummi) which resembles gum arable ; and in the discoveries 

 of Kirchoff (Schweigger's Journal, 1815, xiv, 389) that dilute acids change starch into a 

 gum and grape-sugar, and that gluten, and also a substance of germinating barley that 

 can be extracted by water, and which acts like weak acid, act likewise. The substance from 

 barley was thought by Kirchoff to be the albuminous matter, or the gluten, of the grain. 

 The records of these investigators received full confirmation by contemporaneous workers. 

 Several years later De Saussure (Ann. de chim., 1819, xi, 379) found that when starch- 

 paste was set aside for two years, not only were gum and sugar formed, both of which 

 could be extracted by cold water, but also two other bodies were present, one of which he 

 named amidine and the other ligneux amylacee. Amidine was obtained from the residue 

 by solution in hot water; the hgneux amylacee, so-called because of its resemblance to cel- 

 lulose, was found to be insoluble in both hot and cold water. Amidine was also distin- 

 guished by its giving a blue reaction with iodine. In 1825 Raspail (Ann. d. sciences natu- 

 relle, Oct., Nov., 1825; Mars, 1826; quoted by W. NageH, loc. cit.) carried out experiments 

 in which he heated dry starch on an iron plate, and then added water and tartaric acid 

 to the baked grains that had been placed on the stage of the microscope. He found, as had 

 a number of the earlier investigators, that the grains consist of an inner part and an integu- 



