LECITHIN. 21 



Lecithin is a complex fat of wide distribution. It is a constant 

 constituent of protoplasm, and is found both in the animal and 

 vegetable 1 world. In the animal tissues, it is found principally in 

 the brain and nervous tissues, where it is probably a decomposition 

 product of a more complex substance originally called protagon by 

 Liebreich ' 2 (see section on " Chemistry of Nervous Tissues ") ; in yolk 

 of egg; 3 and in blood corpuscles. 4 Lecithin is found in all organs 

 composed of cells, and also in certain secretions, namely, semen, bile, 

 and milk. 



Lecithin is a yellowish white, waxy, hygroscopic solid, soluble in 

 ether and in alcohol ; it swells and forms a kind of emulsion with 

 water. When ignited it burns and leaves a residue of metaphosphoric 

 acid. Its most important compounds are those of its hydrochloride 

 with platinum chloride (C 44 H 90 NP0 9 Cl) 2 +PtCl 2 , and with cadmium 

 chloride which has a corresponding formula. 5 



Montgomery 6 showed that when water, glycerin, and other reagents 

 were added on a microscopic slide to impure lecithin (or protagon, as he 

 termed it), prepared from egg-yolk, snake-like forms shoot out, bending 

 and curling and even simulating nerve fibres or nerve cells. On 

 cooling a solution of lecithin in alcohol, it separates out in crystal- 

 line clumps. On decomposition by alkalis, it yields glycero-phosphoric 

 acid, a fatty acid, and an alkaloid choline. 



Choline is an ammonium base, and has the following constitution: 



f(CH 3 ) 3 ] 



N CH, CH,OH [ = C 5 H 15 N0 2 



IOH J 



It is therefore trimethyl-oxyethyl-ammonium hydroxide; its name 

 is derived from the fact that it was first separated from the lecithin of 

 the bile. Its synthesis was accomplished by Wurtz 7 from ethylene 



tetronerythrin Wiirm, Ztschr. f. wissensch. Zool., Leipzig, 1871, Bd. xxxi. S. 535 ; 

 Merejkowski, Compt. rend. Acad. d. sc., Paris, 1881, tome xciii. p. 1029 ; MacMunn, Proc. 

 Birmingham Phil. Soc., vol. iii. p. 351 ; Proc. Roy. Soc. London, 1883, No. 226, p. 17 ; 

 Halliburton, Journ. Physiol., Cambridge and London, 1884, vol. vi. p. 324 ; Krukenberg, 

 Centralbl. f. d. med. Wissensch., Berlin, 1879, Bd. ix. S. 705. On serum lutein 

 Krukenberg, Sitzungsb. d. Jenaisch. Gescllsch.f. Med. u. Naturu:, 1885; Halliburton, Journ. 

 Physiol., Cambridge and London, 1885, vol. vii. p. 324. On saponification of lipochromes 

 Kiihue, loc. cit. ; Maly, Afonatih. d. Chem., Wien, 1881, Bd. ii. S. 351 ; Bein, Ber. d. 

 deutscli. chem. Gcscllsch., Berlin, 1890, Bd. xxiii. S. 204. On carrotin Husemann, Ann. d. 

 chem., Leipzig, Bd. cxvii. S. 200 ; Arnaud, Compt. rend. Acad. d. sc., Paris, tome cii. 

 p. 119; civ. 1293. New biggin, "On Crustacean Pigments," Journ. Physiol., Cambridge 

 and London, 1897, vol. xxi. p. 237. 



1 On the subject of lecithin and choline in vegetable oils, etc., see Heckel and 

 Schlagdenhauft'en, Compt. rend. Acad. d. sc., Paris, tome ciii. p. 188 ; Jacobson, Ztschr. f. 

 physiol. Chem., Strassburg, Bd. xxiii. S. 33 ; Schulze, ibid., Bde. xi. S. 365 ; xii. S. 441 ; 

 xvii. S. 204 ; J. Stoklasa, Ber. d. deutsch. chem. Gesellsch., Berlin, 1896, Bd. xxix. S. 2761. 



2 Ann. d. Chem., Leipzig, Bd. cxxxiv. S. 29. 



3 Gobley, Journ. de pharm. et chim., Paris, tomes xi., xii.. xvii., xviii. ; Parke, 

 Hoppe-Seyler's "Med. Chem. Untersuch.," Berlin, Heft 2. S. 213 ;'Hoppe-Seyler, ibid., S. 

 215 ; Diaconow, ibid., S. 221 ; Centralbl. f. d. med. Wissensch., Berlin, 1868, S. 2. 



4 Gobley, Journ. de pharm. et chim., Paris, tome xxi. p. 250; Hermann, Arch, 

 f. Anat. u. Physiol., Leipzig, 1866, S. 33; Hoppe-Seyler, "Med. Chem. Untersuch.," Berlin, 

 Heft 1, S. 140 ; Jiidell, ibid., Heft 3, S. 386. 



5 The formation of these compounds enables one to prepare lecithin in a pure form, the 

 metal being subsequently got rid of by sulphuretted hydrogen. 



(i "On the Formation of So-called Cells," London, 1867. 



7 Ann. d. Chem., Leipzig, 1868, Supplement, Bd, vi. S, 116 and 197 ; see also Bayer, 

 ibid., Bd. cxl. S, 306, 



