P. A. Levene and C. J. West 113 
of amino nitrogen. Thus the task of the preparation of lecithin 
having a composition required by the theory and at the same 
time free of impurities has not yet been accomplished. Efforts 
in this direction are now in progress in this laboratory. 
However, the present finding has a great significance because 
of its bearing on the structure of cephalin, and the work is pre- 
sented in its present incomplete state because of this significance. 
The remarks made earlier in this communication regarding leci- 
thin apply also to cephalin. On the basis of recent work on the 
hydrolytic products of the substance, a certain structural formula 
has been assumed. This formula requires an elementary com- 
Peete or eG, 956.17, H’— 10:57) N 91.88) ande l= 417, 
However, all samples analyzed, beginning with Thudichum and 
up to the present by the most recent investigators,!° consistently 
had the average composition of C = 60.00, H = 9.30, N = 1.80, 
and P = 3.80. 
On the basis of these considerations, one may argue that if 
cephalin and lecithin both had the composition required for them 
by the theory, then a mixture of the two should possess practi- 
cally the same elementary composition as either one of them in 
the pure state. On the other hand, if lecithin possessed the com- 
position assumed by the theory and cephalin that found empir- 
ically, then a mixture containing 80 per cent of the former and 
. 20 per cent of the latter should possess a carbon content of 64.56 
per cent instead of 65.35 per cent. Conversely, if a mixture of the 
two reduced substances posses.ed an elementary analysis of C = 
65.30, H = 11.20, N = 1.75, P = 3.85, it would justify the conclu- 
sion that both lecithin and cephalin possess the composition 
assumed for them by the theory. 
The material analyzed by us contained 80 per cent of lecithin 
and 20 per cent of an impurity. It was found that the material 
yielded on hydrolysis besides the choline also the base amino- 
ethanol. Hence it was reasonable to assume that the 20 per cent 
of impurity consisted of cephalin. If cephalin had the composi- 
tion found by experience then a substance consisting of 80 per 
cent of hydrolecithin and 20 per cent of cephalin should have an 
elementary composition of C = 64.56, H = 10.49, N = 1.75, P = 
10 Levene, P. A., and West, C. J., J. Biol. Chem., 1916, xxiv, 41. 
THE JOURNAL OF BIOLOGICAL CHEMISTRY, VOL. XXXIII, NO. 1 
