NON-AZOTIZED PRINCIPLES. 19 



to form those substances, whose composition is, under the 

 circumstances, most stable. 



The organic compounds existing in the human body may 

 be arranged in two classes, namely, the azotized, or nitro- 

 genous, and the non-azotized, or non-nitrogenous principles. 



The non-azotizcd principles include the several fatty, 

 oily, or oleaginous substances, as margarin, olein, stearin, 

 cholesterin, and others. In the same category of non- 

 nitrogenous substances may be included lactic and formic 

 acids, animal glucose, sugar of milk, etc. 



The oily or fatty matter which, enclosed in minute cells, 

 forms the essential part of the adipose or fatty tissue of 

 the human body, and which is mingled in minute particles 

 in many other tissues and fluids, consists of a mixture of 

 margarin and olein, with a minute quantity of palmitin ; 

 the proportion of the former being the greater the higher 

 the temperature at which the mixture congeals, and the 

 firmer the mass is when congealed. The animal fats, or 

 suets, that are firmer than human fat, contain also a sub- 

 stance named stearin. Each of these fats is composed of 

 an acid margaric, oleic, stearic, or palmitic, in combina- 

 tion with a base glycerin. Stearin melts under ordinary 

 circumstances at 144 F., margarin at 116, palmitin at 

 1 1 8, olein at 25. Human fat is a clear yellow oil, of 

 which different specimens congeal at from 45 to 35. 

 Margarin, when deposited from solution in alcohol, crystal- 

 lizes in pearly scales ; and microscopic tufts or balls of 

 fine needle-shaped crystals of margaric acid are often 

 found in fat- cells after death, especially in the fat of 

 diseased parts and of old people. 



Cholesterin, a fatty matter which melts at 293 F., and is, 

 therefore, always solid at the natural temperature of the 

 body, may be obtained in small quantity from blood, bile, 

 and nervous matter. It occurs abundantly in many biliary 

 calculi ; the pure white crystalline specimens of these con- 

 cretions being formed of it almost exclusively. Minute 



