THE CKPHAT.INS 445 



that an unsaturated acid conijooncnt must be present in such a thromboplas- 

 tic agent, the fact that only stearic acid is present in the lysocephalin would 

 explain the ineffectiveness of the latter. 



Lysocephalin also has a strong hemolytic activity, although Magistris"'' 

 attributes this effect to a contamination of the preparations with lysoleci- 

 thin. It is evident that this field of endeavor requires more experimental 

 work before a clear picture will be available, especially in view of the recent 

 demonstration that the cephalin fraction is made up of a mixture which 

 contains at least three independent molecular complexes. 



f. Distribution of a- and /3-Cephalins. The method for the fractiona- 

 tion of a- and ;S-lecithin employed by Welch^^ has also been used for the 

 determination of the distribution of the a- and /3-forms of cephalin. The 

 distribution of the isomers in the liver, heart, and brain of several species is 

 given in Table 1. The ;5-form of cephalin is found to be predominant in the 

 liver and heart cephalins of the several species studied (liver: beef, rat, 

 guinea pig; heart: beef, cat), while the a- form is present in a larger propor- 

 tion in the case of brain (beef, rat). This is in contradistinction to the dis- 

 tribution of lecithin, the a-form of which is always present in a larger pro- 

 portion. The conclusions as to the distribution in the liver and heart as 

 determined by Welch^^ are in agreement with those of Yoshinaga.^^ 



g. Chemistry and Hydrolysis Products of Phosphatidylethanolamine. 

 Glycerophosphate is also a hydrolysis product of phosphatidylethanol- 

 amine, as well as of lecithin. Phosphorylethanolamine and glycerylphos- 

 phorylethanolamine, which would be comparable to the compounds pro- 

 duced in the hydrolysis of lecithin, have not been characterized. 



(a) Fatty Acids. Thudichum^'*^ demonstrated the presence of stearic, 

 oleic, linoleic, and arachidonic acids in the cephalin molecule. Klenk,^ 

 however, could find no trace of a C20 unsaturated acid in a crude cephalin 

 obtained from brain, but only one which on hydrogenation yielded behenic 

 acid, C22H44O2. 



Cephalin differs from lecithin in having stearic acid as the sole saturated 

 fatty acid. This was first proved by Parnas,^^"''^''* who used a lecithin-free 

 cephalin preparation. Similar results were obtained by Mac Arthur and 

 Burton 2''^ and by Levene and Rolf,-*° as well as by several others. '^•^^•^^^-^^^ 

 Oleic acid is the principal unsaturated acid. Parnas^®" reported 18% of this 

 acid, while MacArthur and Burton™ noted the presence of 50% in their 

 preparation. Levene and Rolf-^^ believed that arachidonic acid also oc- 

 curred as a second unsaturated acid in brain cephalin, but the assumption is 

 in doubt, in view of the subsequent negative results of Klenk. 



2^^ H. Magistris, Biochem. Z., 210, 85-119 (1929). 



2'8 J. Parnas, Biochem. Z., 56, 17-20 (1913). 



"' C. G. MacArthur and L. V. Burton, /. Am. Chem. Soc, 38, 1375-1382 (1916). 



28" P. A. Levene and I. P. Rolf; J. Biol. Chem., 64, 91-100 (1922). 



»i P. A. Levene and C. J. West, /. Biol. Chem., 16, 419-422 (1913). 



