78 MANUAL OF PHYSIOLOGY. 



CLASS B. NON-NITROGENOUS. 

 Group V. CARBOHYDRATES. 



Carbohydrates (general formula, C m H 2u O n ) are bodies in which 

 the hydrogen and oxygen exist in the same proportion as in 

 water, the carbon being variable. The following examples of 

 this group are met with in the textures of the body : 



Grape Sugar (Dextrose}, C 6 H 12 O 6 , occurs in minute quantities 

 in the blood, chyle and lymph. It forms crystals which readily 

 dissolve in their own weight of water. The watery solution has 

 a dextro-rotatory power on the ray of polarized light. When 

 mixed with yeast, the fungus (Saecharomyces cervisice) of the yeast 

 causes alcoholic fermentation of the sugar, whereby alcohol and 

 carbon dioxide are formed. 



Dextrose. Alcohol. 



C 6 H ia 6 =2C a H a O + 2CO a . 



Moderate heat (25 C.) aids the process, and cold below 5 C. 

 checks it ; an excess of either sugar or alcohol stops it. 



The presence of casein or other proteid material, when de- 

 composing, gives rise to lactic fermentation, producing first lactic 

 acid, then butyric and carbon dioxide and hydrogen. 



Dextrose. Lactic acid. Butyric acid. 



C 6 H 12 6 = 2C 3 H 6 3 = C 4 H 8 2 + 2C0 2 + H 4 . 



Milk Sugar (Lactose), Ci 2 H 22 O u -f- H 2 O, isomeric with cane 

 sugar (sucrose). It is the characteristic sugar found in milk. It 

 is not so soluble as dextrose, and does not undergo direct alco- 

 holic fermentation, but under the influence of certain organisms 

 it readily gives rise to lactic acid by lactic fermentation in the 

 same way as dextrose. (See Milk.) 



Inosit, C 6 H 12 O 6 -|- 2H 2 O, is an isomer of grape sugar, which is 

 incapable of undergoing alcoholic fermentation. It is crystal- 

 lizable, and easy soluble in water. It has no effect on the polar- 

 ized ray. It is found in the muscles, and also in the lungs, 

 spleen, liver and brain. 



Glycogen, C 6 Hi O 5 , a body like dextrin, first found in the liver. 

 It gives an opalescent solution in water, and is readily converted 

 into dextrose by an amylolytic ferment, or weak acids. It has a 



