BIOCHEMISTRY OF THE SEXUAL ORGANS 279 



The phosphoric acid constitutes more than half of the ash of the 

 yolk, and it is interesting to note that both the phosphorus and 

 the iron, which are destined to enter into the composition of some of 

 the most important constituents of the cell, such as nucleoproteins, 

 haemoglobin, lipoids, etc., are already present in organic combination. 

 The phosphorus is contained in the phosphorised fats, which constitute 

 about eleven per cent, of the j^olk, and partly in the phosphoprotein 

 •x vitellin, which also contains iron. 



The phosphorised fats are obtained by extracting the yolk, which 

 has previously been freed from water, with cold ether, and precipitating 

 the ethereal extracts with acetone. The precipitate contains the 

 phosphorised fats, while the acetone solution contains the cholesterin 

 which has been extracted together with the phosphorised fats. After 

 all the ether-soluble phosphorised fats have been removed by the 

 ether, further extraction with cold alcohol will remove other 

 phosphorised fats from the yolk. 



The precipitate obtained from the ethereal extract by acetone has 

 often been called lecithin, the name given to the simplest and best- 

 known phosphorised fat. But the work of Erlaildsen,^ and of 

 Thierfelder and Stern,^ has shown, what in the case of nervous tissue 

 had been recognised long ago by Gamgee and by Thudichum, that there 

 are a number of phosphorised fats very similar to lecithin and very 

 difficult to separate from each other. These substances, accompanied 

 always by cholesterin, are widely distributed through the organic 

 world. In fact they are present in every cell, and in almost every 

 animal iluid. This fact alone is sufficient to indicate that the 

 phosphorised fats and cholesterin must fulfil an important function in 

 the life of the cell. 



What this function is has not yet been clearly recognised. We 

 know that anaesthetics such as chloroform, and^ toxins such as snake- 

 venom, exert their action on the cell by virtue of the power of the 

 phosphorised fats to absorb these substances. Lecithin also absorbs 

 or adsorbs sugars, and the resulting sugar-containing adsorption 

 complex is soluble in ether, while pure sugars are not. Ethereal 

 solutions of lecithin take up with great avidity dyes, such as brilliant 

 green, methyl violet, which are soluble in water, but not in ether, and 

 the resulting lecithin dye complex has then the solubilities of a lipoid.^ 

 Many inorganic salts and alkaloids such as quinine are also adsorbed 



^ Erlandsen, " Untersuchungen fiber die lecithinartigen Substanzen des 

 Herzmuskels," Zeitsch. f. physiol. Chem., vol. li., 1906. 



'^ Thierfelder and Stern, "tJber die Phosphatide des Eigelbs," Zeitsch. f. 

 physiol. Chem., vol. liii., 1907. For detailed information see the review of 

 Levene, " Structure and Significance of the Phosphatids," in Physiological 

 Reviews, issued by the American Physiological Society, Baltimore, 1921. 



3 Cruikshank, " The Adsorption of Dyes and Inorganic Salts by Solutions 

 of Lecithin," Jour, of Pathol, vol. xxiii., 192(^ p. 2.30. 



