THE ANIMAL CELL. 45 



takes place and the reaction becomes acid. In putrefying lecithin 

 yields glycerophosphoric acid and cholin; the latter further decom- 

 poses with the formation of methylamin, ammonia, carbon dioxide, 

 and marsh-gas (HASEBROEK). If dry lecithin be heated it decom- 

 poses, takes fire and burns, leaving a phosphorized coke. On 

 fusing with caustic alkali and saltpetre it yields alkali phosphates. 

 Lecithin is easily carried down during the precipitation of other 

 compounds such as the albuminous bodies, and may therefore very 

 greatly change the solubilities of the latter. 



Lecithin combines with acids and bases. The combination 

 with hydrochloric acid gives with platinum chloride a double salt 

 which is insoluble in alcohol, soluble in ether, and which contains 

 10.2$ platinum. 



It may be prepared tolerably pure from the yolk of the hen's 

 egg by the following methods, as suggested by HOPPE-SEYLER and 

 DIACONOW: The yolk, deprived of albumin, is extracted with 

 cold ether until all the yellow color is removed. Then the residue 

 is extracted with water at 50-60 C. After the evaporation of the 

 alcoholic extract at 50-60 C., the syrupy matter is treated with 

 ether and the insoluble residue dissolved in as little alcohol as pos- 

 sible. On cooling this filtered alcoholic solution to 5 to 20 

 C. the lecithin gradually separates in small grains. According to 

 GILSON, a new portion of lecithin may be obtained from the ether 

 used in extracting the yolk by dissolving the residue after the 

 evaporation of the ether in petroleum ether and then shaking this 

 solution with alcohol. The petroleum ether takes the fat, while 

 the lecithin remains dissolved in the alcohol and may be obtained 

 therefrom rather easily by using the proper precautions. 



The detection and the quantitative estimation of lecithin in 

 animal fluids or tissues is based on the solubility of the lecithin (at 

 50-60 C.) in alcohol-ether, by which the phosphoric acid or glycero- 

 phosphoric acid salts which may be present at the same time are 

 not dissolved. The alcohol-ether extract is evaporated, the residue 

 dried and burnt with soda and saltpetre. Phosphoric acid is formed 

 from the lecithin, and it can be detected and quantitatively esti- 

 mated. The distearyllecithin yields 8.798^ P 2 B . This method is, 

 however, not exactly correct, for it is possible that other phosphor- 

 ized organic combinations, such as jecorin (see Chapter VI), may 

 have passed into the alcohol-ether extract. For the detection of 

 lecithin, boiling with baryta-water and the preparation of the 

 double platinum salt of cholin is sufficient. 



The study of the second phosphorized constituents of the cell. 

 the nuclein, is generally pursued with the study of the cell nucleus. 



