28 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



form of dextrin, which he thinks differs from the three forms derived by the action of malt 

 extract, sulphuric acid, and torrefaction, respectively. He views this substance as being 

 in the nature of a starch-building material, and he discusses in this connection the mechan- 

 ism of the formation of the starch-grain. He writes that if one assumes the starch-grain 

 to be an organized body which grows by intussusception there must be present a substance 

 which is soluble and which can enter the grains by osmosis. To serve the function of starch- 

 building no substance is more suitable for the purpose than the various kinds of gums and 

 dextrins, because they on the one hand have the proper solubility, and on the other belong 

 to a group that is isomerous with the insoluble starch-substance, to which group belongs 

 the soluble constituent of starch. This substance which may be built up into starch he 

 states may be termed amylogen, and he holds that, if these views are correct, the question 

 as to the age of the various layers of the starch-grain is solved, for the outer layers must 

 be regarded as the oldest, the greater age and density of the outer layers protecting the 

 soluble contents of the grain. 



Objection was made by Knop (Chem. Centrablatt, 1860, v, 367) to the statement of 

 Jessen and of Delffs that by crushing the starch-grain a gelatinous substance is dissolved 

 out by cold water. Knop believes that the heat generated while rubbing the grain is 

 sufficient to cause gelatinization; but Jessen (Ann. d. Physik u. Chemie, 1864, cxxii, 482) 

 showed later that the ground pulp has a temperature of only 22°, and therefore, in 

 opposition to Knop, not sufficiently high to cause gelatinization. 



Shortly after the investigations of Jessen, Delffs, and Knop, Fliickiger (Zeit. f. Chemie, 

 1861, IV, 104), in a brief article, showed that pulverized starches from various sources are 

 partially dissoh'ed, especially in the presence of calcium chloride. 



According to Dragendorff (Jour. f. Landwirthsch, 1862, vii, 211), starch consists of 

 3 or 4 components: (1) a base which remains after starch has been heated to 60° in a 

 concentrated solution of sodium chloride in a 1 per cent muriatic acid; (2) true starch 

 which is insoluble in cold water; (3) Schultze's amidulin (Delff's amylogen); and (4) 

 occasionally dextrin. 



The influence of light on the formation of starch in chlorophyl granules was studied 

 by Sachs (Botanische Zeit., 1862, xx, 365), who concludes that starch is to be regarded as 

 a product of the assimilative activity of the chlorophyl substance, this activity, being due 

 to the agency of strong light, the starch being built up from CO2 and water in the presence 

 of mineral salts, and being distributed to growing buds and storage centers. He believes 

 that starch formation occurs tlu-ough a series of transformations in the chlorophyl bodies, 

 and that the starch of non-green parts of plants has wandered from the green parts. 



In a later article {ibid., 1864, xxii, 289) Sachs reports the results of experiments in 

 connection with the formation and disappearance of starch in a number of plants. He 

 found that starch which originates in chlorophyl granules under the influence of light 

 disappears when the plant is withdrawn from the light; that starch formed during the day 

 is partly dissolved during the night; and that the entire starch-content disappears in the 

 dark in 48 hours. In accordance with his results, he assumes that during a summer night 

 of 8 hours one-sixth of the starch is dissolved. It would seem, he states, that these reversed 

 processes should throw light on the mechanism of the formation of starch-grains. 



From a study of the chemical properties of starch in relation to various solvents, 

 especially haloid salts, glycerol, and saliva, Kabsch (Zeit. f. analyt. Chemie, 1863, 11, 216) 

 held that the assumption is not justified that starch consists of two different substances, one 

 of which is real starch (granulose) and soluble in saliva (Nfigeli and von Mold), in dilute 

 acids (Melsens), and in cold water after crushing (Reinsch, Jessen, Delffs, and others); and 

 the other substance (cellulose according to Niigeli, and farinose according to von Mohl) 

 insoluble in these media. The grains he found apjiear at first very small, solid, and gran- 

 ular, and during growth become more or less condensed, and arranged in layers which 



