CHAP. X.] THE NERVOUS TISSUES. 427 



tory of Owens College, a series of experiments intended to determine 

 whether Liebreich's protagon existed or not. This preliminary inves- 

 tigation shewed that by Liebreich's process there is always obtained 

 a body having the physical properties of protagon, and containing 

 phosphorus in a proportion sufficiently near to that indicated by him; 

 it was found that the amount of phosphorus in specimens of protagon 

 which had been crystallized from alcohol four or five times, was not 

 smaller than that present in protagon which had only once been 

 crystallized, though a thorough treatment with ether preceded each 

 recrystallization. 



These first experiments, so far as they went, were perfectly satis- 

 factory. It appeared, however, quite essential, before forming a 

 definite opinion, to extend them very considerably, and especially to 

 prove the definite nature of 'protagon by a large number of analyses, 

 indicating not merely the amount of phosphorus, but also that of the 

 other elements present in it. 



This investigation was subsequently carried on by the Author in 

 conjunction with Dr E. Blank enhorn, with the result of proving to 

 their entire satisfaction that protagon is a definite chemical body \ 



Perfectly fresh ox's brains are freed from blood and 

 of BiaiSen- 88 ^ rom a d nei i n g membranes as completely as possible, 

 horn and the and are then digested for many hours (18 to 24) in 

 Author for 85 per cent, alcohol in a large incubator kept constantly 

 preparing at 450 Q The g uid ig filtered wn i lst hotj and the 



insoluble matter is again treated with fresh quantities 

 of spirit, the proceeding being repeated four or five times, as long, 

 indeed, as the filtrate when cooled to deposits a fair quantity of 

 white flocculent precipitate. This precipitate is collected on a filter, 

 and being then transferred to a stoppered bottle is thoroughly and 

 repeatedly agitated with ether, in order to dissolve cholesterin and 

 other bodies soluble in ether 2 . The ether having been removed, 

 first by decantation and then by filtration, the substance left undis- 

 solved by it is first of all dried between sheets of filtering paper 

 in air, and afterwards over sulphuric acid or phosphorus pentoxide. 



1 Gamgee und Blankenhorn, "Ueber Protagon," Zeitschriftf. pliysiol. Chemie, Vol. 

 in. (1879) p. 260. "On Protagon," Journal Physiology, Vol. n. (1879) p. 113. _ 



2 At first we commenced by repeating exactly the process of Liebreich in all its 

 details ; one of the steps of that process we had found fraught with peculiar difficulty, 

 and we soon ascertained that it could be dispensed with without prejudicially affecting 

 the success of the operations. The step to which we refer consists in agitating the 

 freshly pounded brain repeatedly with water and ether at C., so long as the ether 

 dissolves considerable quantities of substance, then filtering and placing the insoluble 

 matter in 85 per cent, alcohol at 45 C. When pounded brain is so treated with water 

 and ether it swells up and the separation of the ether is most incomplete. The process 

 of filtration is one which is attended with great difficulty, even when carried out 

 in the only way in which we found it possible, viz., in the woven bags sold for household 

 purposes, for straining jellies, &c. It was, however, apparent that however prolonged 

 the ether washing, it never succeeded in freeing the brain from cholesterin and other 

 matters soluble in ether, and that the removal of these bodies from protagon was most 

 readily effected at a later stage of the operations. 



