LECITHIN. I. 
““HYDROLECITHIN” AND ITS BEARING ON THE CONSTITUTION 
OF CEPHALIN. 
By P. A. LEVENE anp C. J. WEST. 
(From the Laboratories of The Rockefeller Institute for Medical Research.) 
(Received for publication, December 1, 1917.) 
The recent investigations on the chemical structure of lecithin 
have resulted in many important contributions, all of which 
point to the correctness of the generally accepted view of its 
molecular structure, 
H.C — O — COCi;H3; 
| 
Hoe On COCLHs 
H,C—0P = 0 ne 
ma POE — CH, — CH, — N = (CHs3); 
However, a scrutiny of al] the work on lecithin reveals a re- 
markable incompleteness of each individual investigation. .A 
rigorous proof of the accepted theory requires for lecithin an ele- 
mentary composition of C = 65.60, H = 10.79, N = 1.74, P = 
3.86. It further requires that the nitrogen of the molecule 
should be composed entirely of choline. Hence, lecithin should 
not contain even a part of its nitrogen in the form of free amino 
groups. Still further, it requires a proof of the identity of the 
fatty acids with those accepted by theory, and finally it requires 
the isolation of the glycerophosphorie acid. 
The work up to the present has satisfied many of the require- 
ments. The fatty acids and the glycerophosphoric acid have 
been identified; and MacLean has prepared, at least once, a 
sample of lecithin that was free of amino nitrogen. However, 
this one sample has been incompletely analyzed. All other 
samples of lecithin prepared by various workers contained amino 
111 
