PROTAGON. 607 



are, therefore, as are LESEM, THUDICHUM, WORNER and TmERFELDER, 1 

 and others, of the opinion that protagon does not exist as a chemical 

 individual, but as a mixture of cerebrosides and phosphatides. It is 

 not easy to come to any decision on this disputed question. On the 

 one hand it must be recalled that several investigators call the impure 

 mixture of brain lipoids, protagon, which they obtain from the solution 

 in warm alcohol on cooking, and which is not purified, and this mixture 

 is claimed to be identical, without sufficient basis, with the substance 

 isolated and analyzed by GAMGEE and CRAMER. On the other hand 

 it cannot be denied that certain investigations, especially those of ROSEN- 

 HEIM arid TEBB speak against the chemical individuality of protagon. 

 These investigations do not exclude the possibility that protagon is a 

 loose chemical combination between cerebroside and phosphatide, which 

 like other readily dissociable combinations, exist only under certain 

 conditions or in certain solvents. It is difficult to understand how a 

 mixture of amorphous or only difficultly crystallizable bodies can be 

 so easily crystallized and yield a product, which with proper care, can be 

 recrystallized repeatedly without changing its composition, and physical 

 properties. According to ROSENHEIM and TEBB if the proper quantity 

 is used in solution, a crystalline product can be obtained from the decom- 

 position products of protagon, which has the same specific rotation as 

 protagon and can be repeatedly recrystallized without changing its 

 composition or its optical activity. 2 A further study of these con- 

 ditions would naturally be of great interest. 



As we are not decided whether protagon is only a mixture or is a body 

 contaminated with other substances, it is difficult to decide as to how 

 far the so-called decomposition products exist as preformed constituents 

 of the mixture or whether they are true decomposition products. On 

 boiling with baryta-water protagon yields cerebrosides (see below) and 

 the decomposition products of lecithin, namely, fatty acids, glycerophos- 

 phoric acid, and choline. KOSSEL and FREYTAG found three cerebro- 

 sides, namely, CEREBRIN, KERASIN (homocerebrin), and ENCEPHALIN. 

 According to KOCH 3 the protagon molecule contains cerebroside, lecithin 

 and sulphuric acid (in ester-like combination with the cerebroside) 

 besides excess of cerebroside. Of interest is the finding of KITAGAWA 

 and TmERFELDER 4 that protagon dissolved in methyl alcohol contain- 

 ing chloroform, deposits crusts of cerebron (not pure) after a time at 



1 Lesem, 1. c.; Thudichum, 1. c.; Worner and Thierfelder, Zeitschr. f. physiol. 

 Chem., 30. 



2 Journ. of Physiol., 37; Proc. physiol. Soc., January, 1908, p. 3. 



8 Zeitschr. f. physiol. Chem., 53. 



4 Kitagawa and Thierfelder, ibid., 49; Rosenheim and Tebb, Journ. of Physiol., 37, 

 341 and 348. 



