STEREO-CHEMISTRY AND PHYSIOLOGY 473 



Crum Brown and Fraser 1 have shown that when certain 

 alkaloids containing a trivalent nitrogen atom were allowed 

 to unite with methyl iodide, they gained a new physiological 

 property without losing any of their previous efficiency. The 

 new attribute which they acquire by this increase in the valency 

 of their nitrogen atoms resembles the chief property of curare, 

 for these new methyl iodide addition products have a paralysing 

 action upon the ends of the motor nerves of muscles. Curare 

 itself contains a tertiary base curine, and Boehm 2 has shown 

 that when curine is treated with methyl iodide it yields the 

 quaternary salt curarine, which is two hundred and twenty-six 

 times as poisonous as the mother substance, and which possesses 

 in an acute degree the paralysing properties of curare. The 

 most probable deduction from these results is that the change 

 in the valency of the nitrogen atom lies at the root of these 

 effects ; but we must inquire further whether the consequent 

 change in configuration has not some bearing upon the point. 



Fortunately, the evidence on this subject is already at our 

 disposal. We need only replace the nitrogen atom by some 

 other atom which has the same faculty of changing from the 

 trivalent to the pentavalent condition ; and we are not hampered 

 in our choice in this matter, as no fewer than three other elements 

 have been examined by Vulpian. 3 The substances actually used 

 by him were : (i) tetra-ethyl-arsonium cadmium iodide, (ii) tetra- 

 methyl-arsonium cadmium iodide, (iii) methyl-triethyl-stibonium 

 hydroxide, and (iv) tetra-ethyl-phosphonium iodide : 



C2H 5 CqH 5 CH 3 CH3 C0H5 CoH 5 C2H5 C„H 5 



\/ \ y n y \ y 



As— I.Cdl, As— I.ZnL Sb— OH P— I 



/ \ / \ / N / \ 



CH5 C2H5 CH a CH 3 CH 3 C0H5 C2H5 C2H5 



(i) (ii) (iii)" (iv) 



None of these substances shows the ordinary physiological 

 behaviour of arsenic, antimony, or phosphorus, but all of them 

 have a strong curare-like action, which seems to indicate that that 

 action is due rather to the molecule as a whole than to the nature 

 of the atom at the centre of the complex. 



1 Crum Brown and Fraser, Trans. Roy. Soc. Edin., 25, 707 (1868) ; Proc. Roy. 

 Soc. Edin., 1869, 560. 



2 Boehm, Archiv de Pharmacie, 235, 660 (1897) ; Archivexp. Path. u. Pharmak. 

 6, 101. 



3 Vulpian, Archiv de phys. norm, et pathol., 1, 472; see also Burgi, Archiv. 

 exp. Path, u. Pharmak., 56, 1 01, 



