28 PHYSIOLOGY. 



carbon, hydrogen, and oxygen, the last two in the proportion occurring 

 in the formation of water, two to one. 



The carbohydrates are : 



Glucoses (C 6 H 12 6 ), or monosaccharides. 

 Saccharoses (C 12 H 22 1 ), or disaccharides. 

 Amyloses (C 6 H 10 5 ), or polysaccharides. 



The Glucoses are glucose; or dextrose, or grape-sugar; laevulose, 

 and galactose. The glucoses have three properties which are im- 

 portant for the physiologist to know: physical, chemical, and bio- 

 logical. From the fact that it deviates the plane of polarization to 

 the right, its physical property is demonstrated, whence its name, 

 dextrose. Its chemical property is the reducing of certain metallic 

 salts in the presence of alkalies. Biologically, it ferments under the 

 influence of the zymase of yeast to form carbonic acid and ethylic 

 alcohol. The zymase, an intracellular ferment, is formed in the body 

 of the cell. 



Fig. 5. Yeast Fungus. (After HARLEY.) 



Saccharoses. The saccharoses are saccharose, or cane-sugar; lac- 

 tose, or milk-sugar; and maltose. When saccharose, or cane-sugar, 

 is boiled with a dilute mineral acid, the right-handed polarizing solu- 

 tion of saccharose is transformed into invert-sugar, or is said to be 

 inverted. Invert-sugar is a mixture of equal weights of glucose, a 

 right-handed polarizing agent, and laevulose, which is a left-handed 

 polarizing body. The saccharoses do not reduce the copper salts. 

 The saccharoses are, not directly fermentable by yeast except in this 

 way: (1) when yeast is added, the saccharoses take up water and the 

 soluble ferment of yeast, invertin, changes the saccharoses into glu- 

 cose and laevulose; then (2) the zymase fermentation of the glucose 

 and lasvulose by the yeast-cell, which is not a vital act. 



Lactose, or sugar of milk, is a right-handed polarizing sugar. It 

 reduces the copper salts, but is not fermentable either directly or in- 

 directly by the yeast-ferment. Lactose ferments in the presence of 

 the lactic acid bacillus to form lactic acid. 



Maltose is a right-hand polarizing sugar, reduces copper salts, 



