22 CHEMICAL CONSTITUENTS OF BODY AND FOOD. 
oxide (C 2 H 4 0), trimethylamine N(CH 3 ) 3 , and water. It was at one time 
thought to be identical with the base murine, which Liebreich separated 
from nervous tissues, and the two are closely related ; empirically 
choline (C 3 H 15 ]Si"0 2 ) is neurine (C 3 H 13 NO), plus water. In constitution 
ne urine is trimethylvinylammonium hydroxide. 
Glycero-phosphoric acid is glycerin, in which one of the hydroxy! 
hydrogens is replaced by phosphoric acid, less hydroxyl ; thus — 
HO OH 
C 3 H 5 HO (H 2 P0 3 )HO C 3 H,OH 
HO 0— P0 3 H 2 
(glycerin) (phosphoric acid) (glycero-phosphoric acid) 
If the other two hydroxyl hydrogens are replaced by the radicle of 
stearic acid, we obtain 
CH 2 .0— C 17 H 35 C0 
CH.O— C 17 H 33 CO 
CH,0-Po{™ 
which is distearyl-glycero-phosphoric acid. This is then united to 
choline (less hydroxyl), and we obtain lecithin, or distearyl lecithin, as 
it should be more properly termed ; for other lecithins exist in which 
palmityl, oleyl, or other fatty acid radicles take the place of stearyl. 
The exact manner of the union of the acid with choline is a matter of 
controversy, for up to the present lecithin has not been prepared synthetically. 
Hundeshagen 1 prepared artificially a choline salt of distearyl-glycero-phosphoric 
acid, which is isomeric with lecithin, but which possesses none of its 
characteristic properties. 
The constitution of lecithin is not therefore that of a salt in which choline 
plays a part of the base, as Diaconow - first suggested, but more probably it 
is an ether-like combination, the choline radicle being united to the acid by 
means of the oxygen of the hydroxyl ; the formula for distearyl-lecithin 
would therefore be (Strecker) 3 — 
CH„.0— C ir H 35 GO 
CEL 0— G 17 H 35 CO 
CH 2 .0— PO— O.C 2 HJ 
I (CH 3 U N 
OH HO ) 
The following equation represents the decomposition of lecithin, such 
as occurs on boiling it with alkaline solutions : — 
C 44 H 90 KPO +3H 2 O = 2C 1? H 36 O 2 +C 3 H 9 PO +C 5 H 15 NO 2 
(lecithin) (stearic acid) (glycero- (choline) 
phosphoric acid) 
Lecith-albu ruins. — See p. 69. 
Cholesterin.- — Cholesterin is contained in small quantities in all proto- 
plasmic structures ; it is also found in blood corpuscles and in bile. It is a 
large constituent of sebum and similar oily secretions of the skin. In 
nervous tissues it is an especially abundant constituent of the white sub- 
stance of the medullary sheath. It may be prepared 1)}' making a hot 
1 Journ.f. prakt. CJtcm., Leipzig, 1883, Bd. xxviii. S. '219 ; see also E. Gilson, Ztschr. f. 
physiol. Chiiii., Strassburg, Bd. xii. S. 585. 
2 Cenlralbl. f. d. vied. Wissensch., Berlin, 1868. 
3 Ann. (/. Chan., Leipzig, 1868, Bd. cxlviii. S. 77, 
