158 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



]!)()1, XXXVII, 2836), Berth(4()t and Gaudcchon (Compt. rend., 1890, ex, 1690), Usher 

 and Priestly (loc. cit.), and Fenton (Jour. Chem. Soc, 1907, xci, 687). In the investiga- 

 tion of Bach, Berthelot and Gaudechon, Usher and Priestlj', and Fenton formaldehyde 

 was found, and in several forinic acid was noted. "Various other substances have been 

 used by chemists in the synthesis of formaldehyde, and other instances might be given 

 which have bearing upon aldehyde formation in plants. 



If sugar can be reduced to aldehyde in titro we are justified in assimiing that the reverse 

 may be brought about under proper conditions. This finds confirmation in the investi- 

 gations of Konig, Spieckmann and Ohg (Jour. Chem. Soc, 1903, lxxxiv, 386), who found 

 that bacteria (belonging to the tj^pe of Bacillus coli conummis) in a solution of glucose 

 actually form acetic aldehyde and other compounds; and in those by Renard (Ann. d. 

 chim. e. phj^s., xvii, 321), who records that glucose when subjected to electrolysis in dilute 

 sulphuric acid yields among its products trioxymethylene, which in turn is changed into 

 formaldehj'de, and that a reversal can be brought about so that formaldehyde is trans- 

 formed into sugar. 



Other successful experiments in the synthesis of sugar in vitro have been reported by 

 a number of investigators, as for instance, Loew (Jour. f. prakt. Chemie, 1886, xxxiii, 

 321; Ber. d. d. chem. Gesellsch., 1889, xxii, 475), Fischer (Untersuchungen u. Kolilenhj'- 

 drate ii. Fermente, Berlin, 1909 — a collection of papers that appeared in the Ber. d. d. 

 chem. Gesellsch., from 1884 to 1908), Lob (Zeit. f. Electrochemie, 1907, xii, 282, Biochem. 

 Zeit., 1907, XII, 78), Euler (Ber. d. d. chem. Gesellsch, 1906, xxxix, 39,45), Slosse (Bull. d. 

 I'Acad. roy. d. Belg., 1906, xxxv, 547), and Berthelot (Compt. rend., 1903, cxxvi, 610). In 

 some of these investigations intermediate bodies, such as a-acrose, o-acrosazone, i-fructose, 

 /-mannitol, i'-mannose, ?-mamionic acid, d-mannonic acid, Z-gluconic acid, and rf-gluconic 

 acid are recorded in the synthesis of glucose. The e^•idence, then, is conclusive that not 

 only may saccharine substances be formed from formaldehyde, but also sugar that cor- 

 responds with decomposition products of starch and glj'cogen. Glucose, as already stated, 

 has been converted into isomaltose. JMoreover, ha^'ing glucose as an initial substance, one 

 may obtain from it by appropriate methods in vitro le\iilose, mannose, and other saccha- 

 rine substances. 



Of incidental interest is the fact discovered by Mayer (Zeit. f. phj'siolog. Chemie, 

 1903, xxxviii, 135) that glycollic aldehyde is eliminated bj^ rabbits in the form of glucose. 

 The fact tliat aldehydascs which oxidize aklehydcs ha\e been foimd in plants and also 

 in the li^■er and other organs of animals is not without significance. Gautier suggested 

 years ago that certain glucosides, such as arbutin and salicin, may be derived from formal- 

 dehyde by the addition of hydrogen by molecular condensation and dehj'dration. 



It has also been shown that plant substances maj' be broken down with the formation 

 of aldehyde, as for instance, salicin into helecin and this into salicylic aldehyde or glucose, 

 and amj'gdalin into benzoic aldehj'de, glucose, and hydrocj'anic acid. Acetic aldehj'de 

 is produced in acetification, and in wines, etc. ; and it is formed in the animal body as a 

 decomposition product. There are quite a number of both plant and animal substances 

 which by oxidation yield forms of aldehyde. In fact, instances of this character which 

 have for their indication a suggestion that aldehydes are among the plant metabolites 

 utilized in carbohych'ate and other forms of metabolism might be considerably multiplied. 

 In the animal organism starch is not merely reduced to the glucose stage, but ultimately 

 to carbon dioxide and water. In other words, when diastatic enzymes cease their decom- 

 posing actions other enzymes wliich cause further hydrolysis, or simple molecular splitting, 

 oxidation, etc., come into play, by the agency of which a considerable number of products 

 are formed, among which are included alcohol and its aldehyde. 



"\Miether or not aldehj'de is formed in plants is a matter yet under discussion. E^•idence 

 in fa\'or of the presence of this substance in plants has been offered in the investigations 



