20 LECTURE II. 



positions may be effected by ferments (emulsin, myrosin, betulase, etc.) 

 as well as by chemical reagents. Thus, for example, amygdalin breaks 

 down by the action of emulsin into two molecules of grape-sugar, one 

 molecule of benzaldehyde, and one of hydrocyanic acid: 



C2oH 2 7NOii + 2 H 2 O = 2 C 6 H 12 O 6 + C 6 H 5 CHO + HCN. 



The structure of these compounds has been cleared up perfectly by Emil 

 Fischer, 1 who succeeded in making sugar combine with alcohol and similar 

 substances by the mere action of dilute hydrochloric acid. 2 The glucosides 

 are in fact compounds perfectly analogous to the polysaccharides, both 

 being formed by the combination of two molecules of simpler compounds 

 with loss of water, although in the former case the molecules reacting are 

 unlike, whereas in the case of polysaccharides only sugar molecules are 

 concerned. Not only monosaccharides, but polysaccharides take part 

 in the formation of true glucosides, as Emil Fischer showed in the case 

 of amygdalin. 3 Such observations are of great value for biology, as they 

 permit us to consider the formation of such large classes of substances 

 from a single point of view. 



The significance of the glucosides in the narrower sense of the economy 

 of the animal organism has up to the present time been but slightly inves- 

 tigated. Without doubt a part of the sugar contained in the organism is 

 in such a form, and perhaps this enables such sugar to escape combustion. 

 It is only recently that such substances have been carefully studied. The 

 investigations of Thierfelder 4 upon cerebron, a substance isolated by 

 means of indifferent solvents from the human brain, may be mentioned in 

 this connection. On being subjected to hydrolysis this substance took up 

 two molecules of water and formed one molecule of cerebronic acid, one of 

 sphingosine and one of galactose: 



C 48 H93N0 9 + 2 H 2 O = C2 5 H 5 oO3 + Ci 7 H 35 NO 2 + C 6 H 12 6 . 



A similar glucoside is the glycoproteid prepared by Schulz and Ditthorn 5 

 from the albuminous glands of the frog, which on being subjected to 

 hydrolysis yields among other products an amido-sugar, galactosamine, a 

 result which is closely analogous to the finding of glucosamine by Fried- 

 rich Miiller 6 in the mucin substances of the human respiratory organs. 



1 Ber. 26, 2400 (1893). 



2 For example: C 6 H 12 O 6 + CH 3 OH = C 6 H n O 6 . CH 3 + H 2 O. 



3 Emil Fischer: Ber. 28, 1508 (1895). From amygdalin the yeast-enzyme splits off 

 one molecule of sugar, and forms a new glucoside called mandelonitrile-glucoside, 

 which emulsin decomposes completely into sugar, benzaldehyde, and hydrocyanic acid. 



4 Z. physiol. Ch. 43, 21 (1904) and 44, 366 (1905). 



5 Ibid., 29, 373 (1900); 32, 428 (1901). 



6 Sitzungsber. Gesellsch. Forderung gesamt. Naturwissensch. zu Marburg. 1896, 

 6; 1898, 6. 



