304 On so-called " Protagon " 



be made in order to keep the original theory alive. There is now no doubt 

 that lecithin, to quote only one of the supposed derivatives of " protagon," 

 occurs independently in brain, and besides in no way enters into the 

 composition of " protagon." If we consider the diversity of the mixtures of 

 lipoids occurring in other organs (as demonstrated by the recent researches 

 of Erlandsen on the lipoids of the heart, of Bang and others on those of 

 the blood, of Thierfelder and Stern and of Frankel on those of the 

 egg), there seems to be no justification for the assumption that the lipoids 

 of the brain, the most complex organ, should be derived from one uniform 

 substance, " protagon." In view of the clear evidence against it, we 

 think, therefore, that the time, has arrived to dismiss finally the primitive 

 " protagon " idea as unfounded and contrary to modern conceptions and 

 knowledge. It has for the last forty years unfortunately retarded pro- 

 gress in the investigation of the chemistry of the nervous tissues, instead 

 of stimulating it. We are forced by the results of our prolonged study 

 of the question to repeat our previous conclusion : 



"Protagon" is a heterogeneous mixture, and the term " pro- 

 tagon " has only a historical justification. 



The expenses of this research have been in part defrayed from a grant 

 from the Government Grant Committee of the Royal Society. 



DESCRIPTION OF PLATE. 



Fig. 1. Crystals of sphingomyelin, x 70. Polarised light : crossed nicols. 

 Fig. 2. Crystals of phrenosin. x 88. Polarised light : crossed nicols. 

 Fig. 3. Crystals obtained from "protagon" after fusion, x 130. Polarised light ; 

 crossed nicols. 



