io TEXT-BOOK OF PHYSIOLOGY 



beet, Indian corn, etc. It crystallizes in large monoclinic prisms. It is 

 soluble in water and in dilute alcohol. Saccharose has no reducing power on 

 cupric hydroxid, and hence its presence cannot be detected by Fehling's 

 solution. It is dextro-rotatory. Boiled with dilute mineral, as well as 

 with organic acids, saccharose combines with water and undergoes a change 

 in virtue of which it rotates the plane of polarized light to the left, and hence 

 the product was 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 in the fol- 

 lowing equation: 



C 12 H 22 O n + H 2 = C 6 H 12 6 +C 6 H 12 O a 



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 undergoes inversion, as pre- 

 viously stated, after which it is readily fermented, yielding alcohol and 

 carbon dioxid. 



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

 malia, 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-rotatory. It reduces cupric hydroxid, 

 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 expressed in the following 

 equation : 



C 12 H 22 U + H 2 = 4 C 3 H 6 3 



Lactose + Water Lactic Acid. 



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



Lactic Acid = Buytric 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. The change is expressed by the following equation: 



2C 6 H 10 O 6 + H 2 O - C 12 H 22 O n 



Starch. Water. Maltose. 



Maltose crystallizes in the form of white needles, which are soluble in 

 water and in dilute alcohol. It is dextro-rotatory. In the presence of 

 ferments and dilute acids maltose undergoes hydration and decomposition, 

 giving rise to two molecules of dextrose. It has a reducing action on cupric 

 hydroxid. Fermentation is readily caused by yeast, but whether directly 

 or indirectly by inversion is somewhat uncertain. 



Osazones. All the sugars which possess the power of reducing cupric 

 hydroxid are capable of combining with phenyl-hydrazin, with the formation 

 of compounds termed osazones. The osazones so formed are crystalline 

 in structure, but have different melting-points, varying degrees of solubility 

 and optic properties, all of which serve to detect the various sugars and to 

 distinguish one from the other. Of the different osazones, phenyl-gluco- 



