BIOCHEMISTRY OF THE SEXUAL ORGANS 267 



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 ceU, such 

 as nucleoproteins, haemoglobin, Hpoids, &c., are already present 

 in organic combination. The phosphorus is contained in the 

 phosphorised fats, which constitute about 11 per cent, of the 

 yolk, and partly in the phosphoprotein 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 recent 

 work of Erlandsen,^ 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 great 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 fluid. This fact alone is sufiicient to in- 

 dicate that the phosphorised fats and cholesterin must fulfil 

 an important function in the fife of the cell. 



What this function is has not yet been clearly recognised. 

 We know that anaasthetics 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. 



1 Erlandsen, " Untersnohungen Uber die lecithinartigen Substanzen des 

 Herzmnskels," Zeitschrift f. physiol. Chemie, vol. li., 1906. 



» Thierfelder and Stern, " tjber die Phosphatide des Eigelbs,'' Zeitschrift 

 f. physiol. Ohemie, vol. liii., 1907. 



