1881.] Dr. J. L. W. Thudichum. Note on Protagon. 283 



prepared by Dr. Gamgee, I beg leave to submit the following brief 

 statement. 



In order to decide whether " Protagon," as described in 1864 by 

 Oscar Liebreich, is really a definite chemical body, a true immediate 

 principle of the brain, it is of course essential to know whether the 

 substance, prepared as Liebreich directs, does or does not contain 

 other matters than those for which he accounts in his formula of 

 " protagon ;" and on this question (or rather on part of it) Professors 

 Gamgee and Roscoe have joined issue with me before the Royal 

 Society. 



My contention for some years had been that Liebreich's " protagon" 

 does always contain matters which are foreign to its alleged formula, 

 that it contains them in ponderable quantity, and, among them, notably 

 potassium : and a year ago, in my " Annals of Chemical Medicine," I 

 published details of many analyses to show that, in connexion with 

 trifling differences in the extraction-process, the proportion of potas- 

 sium in different specimens of "protagon" could be made to range 

 from a trace to If per cent. — See op. cit., Art. XIX. 



This position of mine Dr. Gamgee sought to refute before the 

 Royal Society by adducing a note from Professor Roscoe to the effect 

 that Professor Roscoe, having examined spectroscopically the car- 

 bonised residue of a certain gram of "protagon," had found in it only 

 a quantity of potash which he estimated not to exceed 20 ^ 00 part 

 of the whole. See " Proc. Roy. Soc," vol. 30, p. 111. 



On this challenge I submitted to the Society that Professor Roscoe's 

 examination had at any rate established as fact the presence of potas- 

 sium in the " protagon," and that, for reasons which I stated, the 

 quantity of the potassium could not be rightly inferred from any such 

 examination as that which Professor Roscoe had made. See " Proc. 

 Roy. Soc," vol. 30, p. 278. 



Professor Roscoe, apparently in answer to that criticism, has now 

 brought before the Society the result which he obtained in a second 

 examination. Having, in this examination, analysed 5 grms. of 

 " protagon" with regard to the potassium contained in it, he reports 

 that he found it to contain potassium in the proportion of - 0236 per 

 cent. See " Proc. Roy. Soc," vol. 30, p. 365. 



My reason for asking leave to trouble the Royal Society with the 

 above recapitulation, and with a few words of comment on the present 

 state of the case, is, that Professor Roscoe, in closing his recent com- 

 munication to the Society, alludes to certain fresh spectroscopic expe- 

 riments which he has made, and says that they have convinced him of 

 the correctness of the conclusions contained in his original letter. I 

 do not myself quite understand in what sense Professor Roscoe intends 

 that statement, seeing that his later examination of " protagon " had 

 yielded him nearly seven times as much potassium as he had originally 



