1006 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



When levulose is fed to a diabetic patient, it may be burned, though power to 

 burn dextrose has been lost. 1 



H OHOHH 

 cZ-Galactose, CH 2 OH C C C C CHO. This is found combined 



OHH H OH 



with proteid in the brain, forming the glucoside cerebrin. It is produced 

 together with dextrose in the hydrolytic decomposition of milk-sugar. It does 

 not undergo alcoholic fermentation, at least not with Saccharomyces apiculatus. 

 When fed it is not converted directly into glycogen, but through its burning 

 it spares the decomposition of some of the dextrose produced from proteid, 

 which latter may of course be converted into glycogen. 2 



THE DISACCHAEIDES, C 12 H 22 O n . 



These are di-multiple sugars in ether-like combination. To cane-sugar and 

 milk-sugar, Fisher has ascribed the following formulae : 3 



CANE-SUGAR. MILK-SUGAR. 



CH 2 OH CH 3 OH CHO 



CHOH CHOH 

 \CHOH CHOH CH CHOH 

 CH O(CHOH n XCHOH CHOH 

 CHOH X^H ^\CHOH CHOH 

 CH 2 OH CH 2 OH CH O CH 2 



Dextrose group. Levulose group. Galactose group. Dextrose group. 



Cane-sugar, or Saccharose. Cane-sugar, obtained from the sugar-cane 

 and the beet-root, is largely used to flavor the food, and likewise assumes 

 importance as a food-stuff. On boiling with dilute acids, cane-sugar is con- 

 verted through hydrolysis into a mixture of levulose and dextrose. The same 

 result is obtained by warming with 0.2 per cent, hydrochloric acid at the 

 temperature of the body. This inversion, therefore, takes place in the stomach. 

 In the intestinal canal the inversion is accomplished through the action of a 

 ferment present in the intestinal juice. Subcutaneous injection of cane-sugar 

 shows that it is not directly converted into glycogen, but that in burning it 

 spares some dextrose coming from proteid decomposition, and this latter is 

 converted into glycogen and may be found in the liver and muscles. But fed 

 per os, cane-sugar is the cause of a large glycogen storage, in virtue of its 

 greater or less conversion into dextrose and levulose in the intestines. 



Milk-sugar, or Lactose. This is found in the milk and in the amniotic 

 fluid. It is probably manufactured from dextrose in the mammary glands, 

 for the blood does not contain it. It is sometimes present in the urine during 

 the last days of pregnancy, and almost always during the first days of lactation. 

 It readily undergoes lactic fermentation, producing lactic acid, which then 

 causes clotting of the milk. This fermentation may take place in the intestinal 

 tract. Boiling with dilute acids splits up milk-sugar into galactose and dextrose. 



1 Loc tit. * C. Voit : Zeilschrift fur Biologic, 1891, Bd. 28, p. 245. 



* Berichte der deutschen chemischen Gesettschaft, 1894, Bd.26, p. 2400. 



