NON-NITEOGENIZED ALIMENTARY PRINCIPLES. 55 



ent properties from those which contain no nitrogen. While 

 the nitrogenized principles are in a state of continual change, 

 so that it is impossible to fix upon any formula as represent- 

 ing their exact ultimate composition, the non-nitrogenized 

 principles are not changed unless by the influence of some 

 other substance known as a ferment, and have a distinct &nd 

 definite chemical composition. The latter not only differ 

 greatly from the nitrogenized principles, but most of the 

 individual articles of this class present distinctive peculiarities 

 in their general properties, reactions, and ultimate composi- 

 tion. Treating of them as alimentary principles, we have 

 now only to do with their general properties, and the changes 

 which they may be made to undergo out of the body. 



Sugar. A great many varieties of sugar occur in food ; 

 and this principle may be derived from both the animal and 

 vegetable kingdom. The most common varieties derived 

 from animals are sugar of milk and honey, beside a small 

 quantity of liver-sugar, which is taken whenever this part is 

 used for food. The sugars derived from the vegetable king- 

 dom are cane-sugar, under which head may be classed all 

 varieties of sugar except that obtained from fruits, and 

 grape-sugar, which comprises all the varieties existing in 

 fruits. 1 In addition, an impure uncrystallizable residue, ob- 

 tained in the manufacture of the different varieties of cane- 

 sugar, called molasses, is a common article of food. The 

 following are the formulae for the different varieties of sugar 

 in a crystalline form : 



Cane-Sugar, C 12 H n O u 



Milk-Sugar, C 12 H 12 O 12 



Grape-Sugar (Glucose), C 12 H 14 O 14 



All varieties of sugar have a peculiar sweet taste; they 



1 M. Buignet has demonstrated the presence of cane-sugar in quite a number 

 of fruits, always, however, in combination with a certain proportion of grape- 

 sugar. (PAYEN, op. tit., p. 241.) 



