INORGANIC ALIMENTARY SUBSTANCES 147 



The fatty acids, with the exception of oleic acid, are derived by 

 oxidation from the monatomic alcohols. Oleic acid, however, belongs 

 to the acrylic series. Glycerin is a triatomic alcohol, being formed of 

 three atoms of hydroxyl with glyceril. The type of the neutral fats 

 is triacetin ; and the fats should be called triolein, tripalmitin and 

 tristearin, for the reason that in the glycerin which enters into their 

 composition, the three atoms of hydrogen of the hydroxyls are replaced 

 by the acid radicles. 



The following are the empirical formulae for the fats found in the 

 body; triolein, C 3 H 5 (OC 17 H 33 CO) 3 ; tripalmitin, C 3 H 5 (OC 15 H 35 CO) 3 ; 

 tristearin, C 3 H 6 (OC 17 H 35 CO) 3 . At the temperature of the body, 

 triolein holds the two other fats in solution ; and the fats of the body, 

 therefore, are composed of the three varieties and are not solid. 



Boiled with an alkali in the presence of water, fats are decomposed 

 into glycerin, which remains free, and the fatty acid, which latter unites 

 with the alkali to form a soap. The following is an example of this 

 decomposition : 



C 8 H 6 (OC 15 H 31 CO) 3 + 3 KHO = C 3 H 6 (OH), + 3 C 15 H 31 CO.OK. 



A similar decomposition takes place under the influence of superheated 

 steam. When a soap is formed, the decomposition is called saponifica- 

 tion ; when no soap is formed, it is called acidification. The pancreatic 

 juice has the property of acidifying fats. 



Shaken up with gummy or mucilaginous mixtures, liquid fats are 

 subdivided into small granules or globules and held permanently in sus- 

 pension. This is called emulsification ; and the form of the fats is 

 changed in this way in digestion. Examples of fatty emulsions in the 

 body are milk and chyle. 



The lecithins are very complex fats, the formula of which is 

 C 42 H 84 NPO 9 . By decomposition they yield glycerin, phosphoric acid, 

 a fatty acid and cholin. These have been called phosphorized fats. 



Cholesterin is a crystallizable monatomic alcohol with the formula 

 C 27 H 46 O. It is found in large quantity in nervous tissue and also exists 

 in the bile, crystalline lens, spleen, protoplasm of cells and in some 

 other situations. It is taken up from the nervous tissue by the blood, 

 separated from the blood by the liver, discharged into the small intestine 

 with the bile and is eliminated in the form of stercorin (C 27 H 48 O). Ster- 

 corin is to be regarded as a product of katabolism, particularly of the 

 nervous tissue. Cholesterin will be treated of more fully in connection 

 with the bile. 



Inorganic Alimentary Substances. It has been shown that all the 

 organs, tissues and liquids of the body contain inorganic matter in 



