116 FATS 



lecithin is attributable to impurities which may nevertheless be 

 phospholipins. Similarly the alleged action of lecithin in "activating" 

 fibrin-ferment (the blood-coagulating ferment), has recently been 

 shown to be due, in fact, not to lecithin but to kephalin. 



In egg-yolk and in a variety of tissues we find another mono-amino- 

 monophosphatid, designated Kephalin which differs from lecithin in 

 being insoluble in alcohol. It is particularly abundant in brain-tissue 

 and may be extracted by dehydrating the tissue with acetone, extract- 

 ing with ether and adding alcohol to the concentrated extract. It 

 may be purified by precipitation with cadmium chloride. It used 

 to be alleged that kephalin differed from lecithin only in the addition 

 of a methyl group, but recent investigations have shown the difference 

 to be much more profound, inasmuch as the nitrogenous base in keph- 

 alin is not cholin, but amino-ethyl alcohol. Besides its great abun- 

 dance in brain-tissues, where it doubtless plays an important role. 

 Kephalin is of very great physiological importance in consequence of 

 the part which it plays in the coagulation of the blood. The recent 

 investigations of Howell and McLean have shown that kephalin 

 possesses in high degree the power of neutralizing the anti-thrombin 

 in the blood and thus permitting the thrombin, or fibrin-ferment to 

 transform fibrinogen into fibrin and bring about coagulation of the 

 blood. Very small amounts of kephalin, therefore, decisively acceler- 

 ate the coagulation of the blood and kephalin is now being utilized 

 extensively for this purpose in surgery. 



Cuorin which is found in heart-muscle is a mono-amino-diphosphatid 

 (P : N = 2 : 1). It is insoluble in alcohol and in acetone, but very 

 soluble in ether, chloroform and benzol. It readily emulsifies in water 

 and on the addition of alkalies the emulsions form clear solutions. 

 The nature of the nitrogenous base in cuorin is not known. It con- 

 tains three fatty acid radicals for every two molecules of phosphoric acid. 



Sphingomyelin, which is found in the brain, is a diamino-monophos- 

 phatid. It is soluble in hot alcohol but sparingly soluble in cold 

 alcohol, and insoluble in ether. It yields on hydrolysis an alcohol of 

 unknown structure, Sphingol instead of glycerol, and it yields' two 

 different nitrogenous bases, namely Neurine and a base of which the 

 structure is not yet completely defined, which is designated Sphingo- 

 sine (see p. 197). 



GLUCOSIDES OF THE PHOSPHOLIPINS. 



If glucose be added to an ether solution of lecithin, the sugar, which 

 is ordinarily insoluble in ether, dissolves and becomes so closely 

 associated with the lecithin that repeated precipitation and resolution 

 do not remove it. We infer that lecithin forms a compound with 

 glucose, which, however, would appear to be a very loose one, since 

 the analyses of various preparations indicate a very inconstant 

 composition. 



