88 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



with oxide of copper were reported by Trommer (Ann. d. Chem. u. Pliarm., 1841, xxxix, 

 300). During the same year Liebig (Ann. d. Chem. u. Pharm., 1841, xlii, 306) stated 

 that the so-called iodide-starch is not a true chemical compound, the starch being merely 

 impregnated with the iodine; and also that wood fiber is not actually changed into starch, 

 as believed by some, by the action of potassium hydi'ate or sulphuric acid. 



Blondeau de Carolles (Jour. f. prakt. Chemie, 1844, xxxiii, 439) recorded in exami- 

 nations of potato starch that the grains are composed of a number of layers wliich have 

 the same nature and composition, but differ from each other by varying density. He 

 notes that starch changes readily at 60 by rubbing the grains; and he also made elementary 

 analyses and prepared several sulphuric-acid products. 



The optical reactions of the starch-grains and of their solution were reported by Bioz 

 (Ann. de chim. et phys., 1844, xi, 100). The grains were found to be doubly refractive, 

 and the solution (solutions of dextrin) to be dextro-rotatory. Fiirstenberg (.Ann. d. Chem. 

 u. Pharm., 1844, 52, 417), in experiments with cereals, recorded the presence of a dextrin 

 similar to that obtained by the action of dilute sulphuric acid or diastase on starch, and 

 that it does not reduce the oxide of copper. 



Fehhng (Ann. d. Chem. u. Pharm., 1845, lv, 13) experimented on starch with dilute 

 sulphm-ic acid and found what he described as 9 different products in different pro- 

 portions according to the strength of the acid and the length of time of the reaction. 

 Fehling's work received support in the investigations of Kalinowsky (Jour. f. prakt. 

 Chemie, 1845, xxxv, 193), who also later reported {ibid., 201) that tannic acid precipi- 

 tates a solution of starch without forming a compound with the starch. 



The pancreatic juice was found by Bouchardt and Dandras (Compt. rend. acad. 

 sci., 1845, XX, 1085) to have the property of saccharifying boiled starch. At the same 

 time Miahle (Compt. rend. acad. sci., 1845, xx, 954, 1485) reported that the methods of 

 Payen and Persoz for obtaining diastase were applicable to the saliva. He filtered the 

 saUva and added to the filtrate from 5 to 6 volumes of absolute alcohol, wliich caused 

 a small amount of white flocculent precipitate, which was collected and dried at room 

 temperature. Tliis preparation he found to be very energetic, 1 part having the power 

 of converting 2,000 times its weight of starch into sugar. Owing to the apparent identity 

 of its properties with those of diastase, and in order to distinguish it from the diastase 

 obtained from plants, he termed it salivary diastase, a term that has fallen into disuse 

 for the preferable name ptyalin. Since that time it has been shown, from the investiga- 

 tions of a large number of observers, that amyloclastic enzymes are very widely distributed 

 throughout both the animal and plant kingdoms and in the various bodily solids and 

 fluids. The preparations of these earlier investigators were, notwithstanding their energy, 

 very impure, and consisted very largely of inert albuminous matter. 



Reissek (Flora, oder allgemeine Botanische Zeitung, 1847, 13), after a careful study 

 of the normal starch-grain and of the metamorphoses which take jilace when the grains 

 are set aside in water for some time, was led to the conclusion that starch-grains must 

 be viewed as special undeveloped cells, and that in the entire series of starch-grains from 

 the various plants known to us there can be found transition forms from the simple homo- 

 geneous, dense grains to the grains whose outer substance has been differentiated into 

 a membrane, and thus formed into definite cell. 



Schulze (Jour. f. prakt. Chemie, 1848, xliv, 178) reported a substance which he 

 thought stood between starch and dextrin, and which was found to be insoluble in cold 

 water but readily dissolved in hot water. He gave to it the name amidulin, wliich sub- 

 stance is jirobably identical with one obtained by Jacquelin by subjecting starch-paste 

 to a temperature of 150. 



The nature of potato starch was studied by Schleiden (Principles of Botany, 1849, 

 11). He found in tests with iodine and solvents that all parts of the starch-grain are affected 



