120 THE CHEMISTRY OF THE TISSUES AND ORGANS, 



Miiller l obtained cerebrin by rubbing brain up with baryta water, 

 so as to form a milky fluid ; this is boiled, and the resulting coagulmn 

 extracted with boiling alcohol ; on cooling, the alcoholic solution deposits 

 cerebrin and cholesterm. The latter is removed by ether, and the former 

 is purified by repeated crystallisation from boiling alcohol. According to 

 Miiller, its formula is C 17 H 33 N0 3 ; according to Parcus, 2 C 80 H 100 N 2 15 . 

 Parcus also obtained two other similar substances (homocerebrin and 

 encephalin) with different formulae. Adopting a slightly different modus 

 operandi, Geoghegan 3 obtained a substance with the formula C 37 H 110 N 2 25 . 

 Thudichum 4 separated three cerebrins, which he named cerebrin 

 (C 34 H 6G N 2 8 ), phrenosine 5 (C 34 H 07 N0 8 ), and kerasine (C 4C H 91 N0 9 ). 

 Gamgee 6 found that, while protagon cannot be separated by the simple 

 action of solvents into lecithin and cefebrin, yet such non-phosphorised 

 substances do exist by its side in the brain, and one which he called 

 pseudo-cerebrin (C 44 H 92 N0 8 ) can be obtained from protagon by the 

 action of caustic baryta. 



The fact that the cerebrins are glucosides was known to Liebreich, 7 

 Diaconow, Otto, 8 Geoghegan, 9 and Thudichum, 10 but it was only within 

 quite recent years that the sugar was identified as galactose, almost 

 simultaneously in this country and in Germany. 11 



The most recent work on the subject is that by Kossel and Freytag, 12 

 who adopt the very appropriate name of cerebrosides for these bodies. 

 They find that these substances are constituents of the medullary 

 sheaths rather than of the axis cylinders. They have especially worked 

 at two, which they obtained by the decomposition of protagon crystals, 

 namely, cerebrin and kerasin. The analyses of these agree very well 

 with those previously published by Thudichum, Parcus, and others. 

 Their molecular weight was investigated by Beckmann's boiling method, 

 and by the examination of their barium and bromine compounds. By 

 treatment with nitric acid they yield not only galactose but also a 

 fatty acid recognised as neurostearic acid by Thudichum, and correctly 

 analysed but not identified by Miiller. It is, in fact, stearic acid, three 

 molecules of which are formed from cerebrin for every two atoms of 

 nitrogen. From all these considerations, the formula given to cere- 

 brin is C 70 H 140 N 2 13 , and to kerasin (the homocerebrin of Parcus), 

 C 70 H 1>38 N 2 12 . 



Similar substances occur in other parts of the body ; thus two 

 separated from pus are named pyosin, C 57 H 110 N 2 15 , or C^R^NgO^ 

 and pyog&twn, C 63 H 128 N 2 19 . These bodies and similar ones separated 

 from testicular cells are components of the cell protoplasm, not of the 

 nucleus (Kossel and Freytag). 



1 Ann. d. Chem., Leipzig, Bd. ciii. S. 131 ; cv. S. 361. 



2 Journ. f. praTct. Chem., Leipzig, Ed. cxxxii. S. 310. 



3 Ztschr. /. pJiysiol. Chem., Strassburg, Bd. iii. S. 332. 



4 Loc. cit. 



5 For recent papers on phrenosine, see Thudichum, Journ. f. prakt. Chem., Leipzig, 

 Bd. liii. S. 49 ; Kossel, ibid., 1896, Bd. liv. S. 215. 



(! Loc. cit. 



"' Virchow's Archiv, Bd. xxxix. S. 183. 



8 Ibid., Bd. xli. S. 272. 



9 Geoghegan stated that the reducing substance had the formula CooH 45 5 ; he termed 

 it cetylid ; cetylid was no doubt a mixture of galactose and fatty acids. 



10 Journ. f. prakt. Chem., Leipzig, Bd. xxv. S. 23. 



11 Thierf elder, Ztschr. f. pJiysiol. Chem., Strassburg, Bd. xiv. S. 209 ; Brown and 

 Morris, Proc. Chem. Soc. London, 1889, p. 167. 



12 Zttchr. f. physiol. Chem., Strassburg, Bd. xvii. S. 431. 



