110 CANE-SUGAR. 



(iii) SeideVs reaction 1 . A small amount (say -03 gr.) of the 

 suspected substance is evaporated to dryiiess in a platinum crucible 

 with a little nitric acid (sp. gr. I'l 1'2) and the residue is treated with 

 ammonia and a few drops of a solution of strontium acetate. If inosit 

 is present a greenish colouration is observed together with a violet 



precipitate. 



THE CANE-SUGAR GROUP. 



1. Saccharose. (Cane-sugar] C^H^On. 



Although it is not found as a constituent of any animal tissue this 

 sugar possesses no inconsiderable interest in view of the fact that it is 

 a food-stuff which is largely consumed by man and may constitute in 

 many cases no small part of the total carbohydrates with which the 

 body is supplied. 



Cane-sugar is chiefly distinguished from the others by the fact that 

 it does not reduce metallic salts, and does not form a compound with 

 phenyl-hydrazin, but the property which is of greatest interest to the 

 physiologist is the ease with which it may be ' inverted ' or converted 

 into equal parts of dextrose and leevulose 



C 12 H 22 O n + H 2 O = C 6 H 12 O 6 (dextrose) + C 6 H 12 6 (Isevulose). 

 This inversion is readily brought about by treatment with dilute 

 mineral acids at 100 or even at 40 or below if the action is more 

 prolonged 2 ; it is also the result of the action of enzymes more especially 

 of invertin from yeast, and is characterised experimentally by the 

 change in the rotatory power of the solution, which from being 

 originally dextro-rotatory becomes laevo-rotatory ; hence the name 

 'inversion.' For cane-sugar (a) D = + 66; for Isevulose (a) D - 100. 

 The rotatory power of the latter is largely dependent upon temperature 

 and concentration. 



When cane-sugar is injected into the blood vessels or tissues of an 

 animal it is eliminated in an unaltered condition and is thus shown to 

 be non-assimilable 3 . On the other hand it may be introduced in large 

 amounts into the alimentary canal without reappearing externally in 

 the urine. From this it may be concluded that it undergoes some 

 change before or during absorption and this change is most probably 

 that of inversion. This change may take place in the stomach, partly 

 under the influence of the acid of the gastric juice but also as the 

 result of the action of a soluble enzyme 4 ; it is even more marked in 



1 Dissertation, Dorpat 1884. Quoted by Fick. (Pharm. Zt. f. Russl.} See 

 Abstr. in Ber. d. d. chem. GeselL Jahrg. xx. (1887), Kef. Bd. S. 320. 



2 Of. Wohl, Ibid. Jahrg. xxm. (1890), S. 2087. 



3 Bernard, Legons de Physiol. exp. T. i. 1855, p. 219. 



4 Leube, Virchow's Arch. Bd. LXXXVIII. (1882), S. 222. Cf. Hoppe-Seyler, 

 Virchow's Arch. Bd. x. (1856), S. 144. Koebner, Diss. Breslau, 1859. Abst. in 

 Henle u. Meissner's Jahresb. 1859, S. 236. 



