THE PHOSPHOLIPINS OR PHOSPHATIDS 113 



infests the Chinese Ash. The most widely employed vegetable wax 

 is carnaiiba wax, obtained from the leaves of the Wax-palm or Car- 

 naiiba-palm which grows in tropical South America. It consists of a 

 complex mixture of esters of higher monatomic alcohols. 



THE PHOSPHOLIPINS OR PHOSPHATIDS. 



In all living tissues and without exception, we find a variety of 

 complex substances resembling the fats in their solubility in organic 

 solvents, and yielding fatty acids, alcohols (usually glycerol), phos- 

 phoric acid and nitrogenous bases when hydrolyzed. These sub- 

 stances constitute the group of Phospholipins, and on account of their 

 constant association in the tissues with cholesterol and cholesterol 

 derivatives they are sometimes included with these in the larger group 

 of Lipoids or fat-resembling substances, the common characteristic 

 of the group consisting in their high solubility in fats and oils, and in 

 the various fat-solvents. The term lipoid, however, is merely a con- 

 venient brief designation of a heterogeneous group of substances 

 which may be chemically unrelated to one another. The phospho- 

 lipins, on the contrary, are a rather well-defined and homogeneous 

 group of chemically related substances. 



The best known and most abundant representatives of the phos- 

 pholipin group are the Lecithins. These substances, which are found 

 in every living cell, yield fatty acids, glycerol, phosphoric acid and 

 choline (=oxyethyl trimethyl ammonium hydroxide) on hydrolysis. 

 One molecule of phosphoric acid is yielded for every molecule of 

 choline, and the phosphorus and nitrogen-contents of these substances 

 stand therefore in the proportion to one another of 1 : 1. The struc- 

 ture of the lecithins is believed to be represented by the formula: 



CHz.O (fatty acid radical) 

 CH.OL (fatty acid radical) 

 CH 2 .0 

 HO - P = O 



C 2 H 4 O 



' / 



N = (CH 3 ) 3 

 \ 



OH. 



The fatty acid radicals consist, as a rule, of palmitic, stearic or oleic 

 acid, but at least one oleic acid radical would appear to be invariably 

 present, since the lecithins exhibit to a very high degree the character- 



8 



