CHAP. X.] THE NERVOUS TISSUES. 425 



Mr Geoghegan 1 has estimated the amount of the hypothetical 

 nuclein in brain at 1*4 grms. per 1000 grms. of brain-substance. 



SECT. 4. THE PHOSPHORIZED CONSTITUENTS FOUND IN NERVOUS 



TISSUES. 



There is no subject in Physiological Chemistry concerning which 

 it is more difficult to give a statement, which would be accepted as 

 correct by those who have devoted their attention to it, than the 

 chemistry of the complex phosphorized fats which exist in the nervous 

 tissue. In the following pages an attempt will be made to give as 

 impartial an account as possible of the present co-ndition of a subject 

 which is eminently in a transition stage. 



PKOTAGON. 



Discovery * n ^ e y ear 18 ^5, ^r Oscar Liebreich published an 



by Liebreich. important paper 2 upon a new proximate principle which 

 he had separated from the brain. Unlike the numerous 

 bodies, possessed of ill-defined properties, which had,, by different 

 writers, received the names of cerebrin, cerebric acid, lecithine, or 

 phosphorized fats, this new body could be extracted by an easy process 

 in a state of purity, and to it, probably as indicating it as the first 

 definitively ascertained specific constituent of brain, Liebreich ascribed 

 the name of Protagon (Trpurayos, leading in advance). 



Mode of ^"he substance was obtained by the following process. 



preparation. An animal was bled to death from the carotid, and a 

 stream of water was passed through the vessels of the 

 head, so as to wash the blood out. The brain, freed from its mem- 

 branes, was then pounded in a mortar and shaken in a flask with 

 ether and water at C. It was allowed to stand at a temperature of 

 0, until the ether had separated, and the treatment with ether again 

 and again repeated. 



The brain-matter having been separated by filtration from ether 

 and water, was digested with 85 per cent, alcohol, at a temperature of 

 45 C. The fluid was filtered hot and allowed to cool at 0C. A 

 flocculent precipitate then separated, which was collected on a filter 

 and treated with cold ether, until it ceased to dissolve cholesterin. 

 The insoluble mass was dried in vacuo, and dissolved in spirit at 45 C. 

 The alcoholic solution was filtered, and allowed to cool very gradually, 

 when protagon separated in the form of microscopical needles, differing 

 a little in arrangement and form according to the concentration of the 



1 Edward G. Geoghegan (aus Dublin). " Ueber die anorganischen Gehirnsalze nebst 

 einer Bestimmung des Nucleins im Gehirn." Zeitschrift f. phys.Chem, Vol. i. p. 330. 



2 Oscar Liebreich, "Ueber die chemische Beschaffenheit der Gehirnsubstanz." 

 Annalen der Chemie und Pharmacie, Bd. cxxsrv. S. 29 44. 



