CHEMICAL COMPOSITION OF THE HUMAN BODY 21 



small quantities, in the blood and lymph. It is the form in 

 which most of the carbohydrates in the body are carried by 

 the blood from one place to another (from intestine to the 

 liver, thence to the tissues, where the physiological combus- 

 tion takes place). Pathologically it appears, often very 

 abundantly, in the urine (diabetes mellitus). 



Glucosamin, C 6 H U O.NH 2 , is a nitrogenous derivative of grape- 

 sugar which is transformed into grape-sugar by the action of nitric 

 acid. It is obtained by the decomposition of chondroitin (a con- 

 stituent of cartilage) or of chitin (a constituent of integuments of 

 arthropods). This transformation is of importance in showing 

 how carbohydrates can be derived from proteids. 



Inosit, C 6 H 12 O 6 , a sweet-tasting substance, does not belong to the 

 sugars, as its carbons form a closed circular chain, six -CHOH 

 groups forming a ring, and is therefore hexahydroxy-benzene. 

 Inosit is soluble in water, insoluble in alcohol and ether, optically 

 inactive, does not reduce nor ferment with yeast, but undergoes 

 lactic-acid fermentation. It crystallizes in prisms, grouped in 

 rosettes. Successively treated with nitric acid, ammonia, and 

 calcium chloride, it leaves, on drying, a rose-red spot. Inosit is 

 found in muscles; its physiological importance is unknown. 



Disaccharides are anhydrid compounds of two monosac- 

 charide molecules of the same or different kinds: 



2(C 6 H 12 (i ) 2 -H 2 = C, 2 H 22 1I . 



In this group belong: 



Cane-sugar = grape-sugar -j- fructose. 



Milk-sugar (lactose) = grape-sugar + galactose. 

 Maltose = grape-sugar + grape-sugar. 



By boiling with acids and by inverting ferments, these- 

 sugars, under the assumption of water, are split up into their 

 components. They are dextrorotatory, reduce (except 

 cane-sugar) and form phenylosazones. Lactosazone melts 

 at 200 ; maltosazone at 208. The disaccharides do not 

 undergo alcoholic fermentation directly. 



Cane-sugar and maltose are important foods. Lactose is 

 also an important food and is of special physiological interest 

 because it is a specific product of the animal body, being 



