PHOSPHATIDES. 239 



quantities of compound esters of lauric, myristic, and stearic acids with radicals 

 of the alcohols, LETHAL, Ci 2 H 25 .OH, METHAL, Ci 4 H 29 .OH, and STETHAL, Ci 8 H 3 7.OH. 



Cetin is a snow-white mass shining like mother-of-pearl, crystallizing in plates, 

 brittle, fatty to the touch, and which has a varying melting-point of 30 to 50 C., 

 depending upon its purity. Cetin is insoluble in water, but dissolves easily 

 in cold ether or volatile and fatty oils. It dissolves in boiling alcohol, but crys- 

 tallizes on cooling. It is saponified with difficulty by a solution of caustic potash 

 in water, but with an alcoholic solution it saponifies readily, and the above-men- 

 tioned alcohols are set free. 



CH 3 



Ethal or cetyl alcohol, CieH^O. = (CH 2 )i 4 , which occurs in smaller quantities 



CH 2 .OH 



in beeswax, and was found by LUDWIG and v. ZEYNEK in the fat from dermoid 

 cysts though this is denied by AMESEDER, 1 forms white, transparent, odorless, 

 and tasteless crystals which are insoluble in water but dissolve easily in alcohol 

 and ether. Ethal melts at 49.5 C. 



SPERMACETI-OIL yields on saponification valeric acid, small amounts of solid 

 fatty acids, and PHYSETOLEIC ACID. This acid, which has, like hypogaeic acid, 

 the composition Ci 6 H 30 2 , occurs also, as found by LjuBARSKY, 2 in considerable 

 amounts in the fat of the seal. It forms colorless and odorless needle-shaped 

 crystals which easily dissolve in alcohol and ether and melt at 34 C. 



BEESWAX may be treated here as concluding the subject of fats. It con- 

 tains three chief constituents: (1) CEROTIC ACID, C 2 6H 8 20 2 , 3 which occurs as cetyl 

 ether in Chinese wax and as free acid in ordinary wax. It dissolves in boiling 

 alcohol and separates as crystals on cooling. The cooled alcoholic extract of 

 wax contains (2) CEROLEIN, which is probably a mixture of several bodies, and 

 (3) MYRICIN, which forms the chief constituent of that part of wax which is 

 insoluble in warm or cold alcohol. Myricin consists chiefly of palmitic-acid 

 ester of melissyl (myricyl) alcohol, CsoHei.OH. This alcohol is a silky, shining, 

 crystalline body melting at 85 C. DUNHAM 4 has found carnaubic acid, C^H^O-. 

 in a phosphatide from the ox kidney. 



2. Phosphatides. 



In close relation to the fats stands a group of esters containing 

 nitrogen, phosphoric acid and fatty__acid radicals. The representative 

 of this group longest known is lecithin. This latter is an ester combina- 

 tion of a nitrogenous base, choline, with a fatty acid-glycerophosphoric 

 acid, and THUDICHUM 5 has shown that a large number of more or less 

 analogous bodies occur in the animal body, especially in the brain. 

 All of these bodies have received the name phosphatides. 



Those phosphatides which contain only one phosphoric acid radical 

 in the molecule are called monophosphatides; those with two such radicals 

 diphosphatides. The monophosphatides may contain one, two or more 



1 Ludwig and v. Zeynek, Zeitschr. f. physiol. Chem. 23; Ameseder, <ibid., 52. 



2 Journ. f. prakt. Chem. (N. F.), 57. 



3 See Henriques, Ber. d. deutsch. chem. Gesellsch., 30, 1415. 



4 Journ. of biol. Chem., 4. 



6 J. L. W. Thudichum, Die chemische Konstitution des Gehirns des Menschen, 

 etc., Tubingen, 1901. 



