70 MANUAL OF PHYSIOLOGY. 



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 dis- 

 solve 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 (Saccharomyces cervisice) of the yeast causes 

 alcoholic fermentation of the sugar, whereby alcohol and carbon- 

 dioxide are formed. 



Dextrose. Alcohol. 



C 6 H 12 6 = 2C 2 H 6 + 2C0 2 . 



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,H 8 2 + 2CO a + H 4 . 



Milk/Sugar (Lactose), C 12 H 22 O n -f H 2 0,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 alcoholic 

 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 

 incapableof undergoing alcoholic fermentation. It is crystal! izable, 

 and easily soluble in water. It has no effect on the polarized ray. 

 It is found in the muscles, and also in the lungs, spleen, liver, and 

 brain. 



Glycogem, C fl H 10 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 

 strong dextro-rotatory power. It can be found in most rapidly 

 growing tissues. (See Glycogenic Function of the Liver.) 



