Chemical Constituents of the Animal Body. 2 1 3 



In view of the chemical constitution of ethyl alcohol, 

 which contains a methyl group, (CH 3 -CH 2 -OH), and of 

 dextrose, in which this group is absent, the chemi- 

 cal mechanism of this biochemical reaction is obscure, 

 and a large amount of work has been devoted to the 

 elucidation. No completely satisfactory explanation, in 

 spite of the amount of research, can be said, so far, to 

 have been offered. It is of interest to note, however, that 

 not all the sugars can undergo alcoholic fermentation. 

 Only the monosaccharoses with three, six, or nine carbon 

 atoms are fermentable with yeast, and only selected in- 

 dividuals amongst these sugars. Of the hexoses, the four 

 naturally occurring individuals, cZ-galactose, c^-mannose, 

 (^-dextrose, and laevulose, are fermentable, and it is of 

 interest to note that all four are closely related as regards 

 their stereometric configuration. It may be recalled that 

 the three last-named all yield the same osazone. 



THE DISACCHA ROSES. 



Cane-sugar or sucrose, the most widely distributed 

 of these sugars, is prepared chiefly from the beet and 

 sugar-cane. On hydrolysis with mineral acids, it under- 

 goes scission into "invert sugar " (p. 192), a mixture of 

 dextrose and Isevulose 



u + H 2 = C 6 H ia 6 + C 6 H 12 6 



It contains eight hydroxyl groups, since on treatment with 

 acetic anhydride and sodium acetate it yields an octacetyl 

 derivative, C 12 H 14 3 (0-CO-CH 3 ) 8 . 



Sucrose also undergoes scission into a mixture of 

 dextrose and Isevulose when treated with the ferment 

 " invertase," which occurs in yeast. 



Maltose, C 12 H 22 O n , is produced from starch when the 

 latter is treated with malt which contains a ferment 



