18 ESSENTIALS OF CHEMICAL PHYSIOLOGY 



appear to have the harmful effect that other sugars produce. Levu- 

 lose gives the same general reactions as dextrose. 



Galactose is formed by the action of dilute mineral acids or 



inverting ferments on lactose or 

 milk sugar. It resembles dextrose 

 in being dextro-rotatory, in reducing 

 cupric hydrate in Trommer's test, 

 and in being directly fermentable 

 with yeast. When oxidised by means 

 of nitric acid it, however, yields an 

 acid called mucic acid (C 6 H 10 O 8 ), 

 which is only sparingly soluble in 

 water. Dextrose when treated in this 

 way yields an isomeric acid i.e. an 

 acid with the same empirical formula, 

 called saccharic acid, which is readily 



FIG. 2,-Inosite crystals. soluble in Water. 



Inosite, formerly called muscle sugar, is found in muscle, kidney, liver, 

 and other parts of the body in small quantities. It is also largely found in 

 the vegetable kingdom. It is a crystallisable substance (see fig. 2) and has 

 the same formula (C H l2 O t .) as the glucoses. It is, however, not a sugar. 

 It gives none of the sugar tests, and careful analysis has shown it has quite 

 a different chemical constitution from the true sugars. It belongs to the 

 aromatic series, and is only included here for convenience. 



DISACCHAEIDES 



Cane Sugar, This sugar is generally distributed throughout the 

 vegetable kingdom in the juices of plants and fruits, especially the 

 sugar cane, beetroot, mallow, and sugar maple. It is a substance of 

 great importance as a food. After abundant ingestion of cane sugar 

 traces may appear in the urine, but the greater part undergoes 

 inversion in the alimentary canal. 



Pure cane sugar is crystalline and dextro-rotatory. It holds cupric 

 hydrate in solution in an alkaline liquid thfct is, with Trommer's 

 test it gives a blue solution. But no reduction occurs on boiling. 

 After inversion it is strongly reducing. 



Inversion may be brought about readily by boiling with dilute 

 mineral acids, or by means of an inverting ferment, such as that 

 occurring in the succus entericus or intestinal juice. It then takes 

 up water and is split into equal parts of dextrose and levulose : 



C J2 H 22 O n +H 2 0=C 6 H 12 6 



[cane sugar] [dextrose] [levulose] 



