CHEMIC COMPOSITION OF THE HUMAN BODY. 13 



detected by Fehling's solution. It is dextro-rotary. Boiled with 

 dilute mineral, as well as organic acids, saccharose combines with 

 water, and undergoes some change in virtue of which it rotates the 

 plane of polarized light to the left, and hence the product is termed 

 invert sugar. This latter has been shown to be a mixture of equal 

 quantities of levulose and dextrose. This inversion of saccharose 

 through hydration and decomposition is expressed by the following 

 equation : 



C 12 H 22 U + H 2 = C 6 H 12 6 + C 6 H 12 6 . 



Saccharose. Water. Levulose. Dextrose. 



Invert Sugar. 



Saccharose is not directly fermentable by yeast, but through the 

 specific action of a ferment, invertin or invertase, secreted by the 

 yeast plant, or the inverting ferment of the small intestine, it under- 

 goes inversion, as previously stated, after which it is readily fer- 

 mented, yielding alcohol and carbon dioxid. 



Lactose is the form of sugar found exclusively in the milk of the 

 mammalia, from which it can be obtained in the form of hard, 

 white, rhombic prisms united with one molecule of water. It is 

 soluble in water, insoluble in alcohol and ether. It is dextro-rotary. 

 It requires cupric oxid, but to a less extent than dextrose. Dilute 

 acids decompose it into equal quantities of dextrose and galactose. 

 Lactose is not fermentable with yeast, but in the presence of the 

 lactic acid bacillus it is decomposed into lactic acid, and finally into 

 butyric acid, as follows : 



C 12 H 22 O 11 + H 2 O = 4C 3 H 6 O 3 

 Lactose. Water. Lactic Acid. 



2C 3 H 6 O 3 = C 4 H 8 O 2 + 2 CO 2 + 2 H 2 

 Lactic Acid. Butyric Acid. Carbon Free 



Dioxid. Hydrogen. 



Maltose is a transformation product of starch, and arises whenever 

 the latter is acted on by malt extract or the diastatic ferments in 

 saliva and pancreatic juice. It can also be produced by the action 

 of dilute sulphuric acid on starch. The change is expressed by the 

 following equation : 



2C 6 H 10 B + H 2 = C 12 H 22 O n . 

 Starch. Water. Maltose. 



