180 ALIMENTATION. 



are not yet familiar. In their relations to the body as alimentary principles, these would 

 not possess much practical interest, even if they had all been isolated and studied ; for all 

 articles of this class are apparently transformed into the same nutritive principles, 

 namely, the albuminoid constituents of the blood. 



Noyi-Nitrogenized Alimentary Principles. 



The important principles belonging to the class of non-nitrogenized matters are the 

 sugars, starch, and fat. From the fact that these are supposed by some to be exclusively 

 concerned in keeping up the animal temperature by the oxidation of carbon, they are 

 frequently spoken of as the carbonaceous or calorific elements of food. They are some- 

 times called hydro-carbons. 1 



In many respects there are marked and important differences between the nitro- 

 genized and non-nitrogenized articles of food ; and whether or not these differences relate 

 to the nutrition of the organism is a question which will be considered in its appropriate 

 place. The production of animal heat, which is supposed by some to be due entirely to 

 the action of non-nitrogenized substances, is closely connected with the function of nutri- 

 tion, and all that is at present known of this general process must be taken into con- 

 sideration in connection with calorification. It is certain, however, that all alimentary 

 and proximate principles which contain nitrogen, excluding the inorganic and some 

 crystallizable organic substances, have very different 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 representing their exact ultimate composition, 

 the non-nitrogenized principles are not changed, unless by the influence of some other sub- 

 stance known as a ferment, and have a distinct and 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 composition. 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 under- 

 go 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 the 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 the liver is used for food. The sugars derived from the vege- 

 table kingdom 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 exist- 

 ing in fruits. In addition, an impure, uncrystallizable residue, obtained in the manu- 

 facture of the different varieties of cane-sugar, called molasses, is a common article of 

 food. The following are the formulas for the different varieties of sugar in a crystalline 

 form : 



Cane- Sugar, da Hn On 



Milk-Sugar, d a H 12 O ]2 



Grape-Sugar (Glucose), da Hu O J4 



All varieties of sugar have a peculiar sweet taste ; they are soluble in water and in 

 alcohol; they are inflammable, leaving an abundant carbonaceous residue and giving off 

 a peculiar odor of caramel ; they are capable of being converted, in contact with fer- 

 ments or with nitrogenized principles, into alcohol and carbonic acid and into lactic 

 acid; they are also capable of other modifications when treated with the mineral acids, 

 or with alkalies, which are interesting more in a chemical than a physiological point of 

 view. Of all the varieties of sugar, that made from the sugar-cane is the most soluble, 



1 The name hydro-carbon is strictly applicable only to the sugars and starch, which are, chemically, hydrates of 

 carbon, containing as they do, carbon, with hydrogen and oxygen in the proportions to form water. 



