IOO THE CHEMICAL COMPOSITION OF THE BODY 



levorotatory, [a] d = 92. Levulose may be crystallized with difficulty in 

 needles. It has a sweet taste. It reduces alkaline solutions of the 

 metallic oxides, but not so much as dextrose, and yields an osazone identical 

 with glucosazone. It undergoes fermentation, but less readily than dextrose. 



Galactose is obtained with dextrose from milk-sugar or lactose on 

 boiling with dilute mineral acids. It is less soluble in water than levulose 

 or glucose. It reduces metallic oxide in alkaline solution, forms a charac- 

 teristic osazone which melts at 193-4 C. and it undergoes slow fermentation 

 by yeast. It is dextrorotatory. 



It is also obtained on hydrolysis of cerebrin, a glucoside occurring in 

 nervous tissue. 



Maltose (malt -sugar) is produced by the action of amylolytic enzymes 

 on starch and glycogen. It crystallizes in small needles, is strongly dextro- 

 rotatory, [a] d = +140.6, reduces alkaline copper solutions much feebler 

 than dextrose, and does not reduce bismuth oxide. It forms a characteris- 

 tically crystalline osazone, melting at 206 C. It is readily soluble in water 

 and only slightly soluble in alcohol. Maltose is not so sweet as cane-sugar. 

 It does not undergo alcoholic fermentation with yeast unless first split into 

 dextrose. On boiling with dilute mineral acids or through the action of 

 inverting enzymes, it is hydrolyzed into dextrose. 



Saccharose (cane-sugar) is obtained from many plants, such as the 

 sugar beet and sugar cane, and from the sap of certain trees, as the sugar 

 maple. It crystallizes in prisms, is soluble in water, and only very slightly 

 soluble in alcohol. Cane-sugar is not directly fermentable by yeast. It is 

 dextrorotary. Saccharose has no reducing action on alkaline copper solution 

 the dextrose and levulose yielded on inversion probably being united 

 together by the aldehyde and ketone radicals, respectively. Similarly, it does 

 not form an osazone. In strong solutions, saccharose acts as a food pre- 

 servative against bacterial or other decomposition through organic agencies. 

 On boiling with dilute mineral acids or through the action of inverting en- 

 zymes, one molecule of saccharose yields one molecule of dextrose and one 

 molecule of levulose. 



Lactose (milk-sugar) is present as the chief carbohydrate of milk. It 

 may be separated from the whey the product remaining after skimming 

 milk and precipitating the proteins therein. It can be prepared in large 

 hard crystals. It is much less soluble in water than cane-sugar, and has but 

 a slightly sweet taste. Lactose is strongly dextrorotatory, [a] d = +52.5. 

 It reduces alkaline copper solution and forms a characteristic osazone. It 

 is not fermented by ordinary yeast; certain bacteria easily convert it into 

 lactic and other simple organic acids. The inverted milk-sugar undergoes 

 alcoholic fermentation readily, and kumiss and kephir, made from mare's 

 and cow's milk, respectively, are prepared in this way. On hydrolyzing by 

 boiling with mineral acids or through the action of inverting enzymes, the 

 lactose is split into dextrose and galactose. 



