474 STUDIES IN GENEEAL PHYSIOLOGY 



It is well known that weak solutions of Na CO 3 increase 

 the irritability of the muscle. NaOH in dilute solution acts 

 in the same way. Strange to say, these effects are generally 

 attributed to the Na. We are dealing in both cases, how- 

 ever, with effects which are brought about solely through 

 the hydroxyl ions (see sec. iii) and which have nothing to 

 do with the Na ions or the Na compounds. So far as I 

 know, this error goes through the whole literature of physi- 

 ology and pharmacology. The chapter of chemical stimula- 

 tion as well as the chapter on pharmacology stand in need of 

 a thorough revision on the basis of the theory of dissociation. 



VIII. THE VELOCITY OF MIGRATION AND THE RELATIVE 

 TOXICITY OF DIFFERENT IONS FOR THE MUSCLE 



It seems to me to be of the greatest interest to compare 

 the relative toxicities of ions in order to discover if any rela- 

 tions exist between these toxicities and the other properties 

 of the ions. 



If I make such a comparison of the toxicity of the ions 

 dealt with in this paper, I do it with two reservations: first, 

 that although the method of determining the toxicity of ions 

 for muscle by determining the threshold of stimulation is 

 superior to the method of Kahlenberg, it is, nevertheless, not as 

 accurate as that of determining the velocity of migration of 

 the ions; secondly, that the observations made thus far refer 

 to only a very limited number of ions. I hope to overcome 

 the latter shortcoming by further experiments. But I do 

 not yet see how the former difficulty is to be overcome. 



The most poisonous ion (of the ions which have been dis- 

 cussed in this paper) for muscle is undoubtedly the hydrogen 

 ion, which has the lowest atomic weight, but the greatest 

 velocity of migration. For the strength of current and the 

 induction apparatus employed by us, 10-15 c.c. of a one-tenth 

 normal HC1, HNO 3 or |H 2 SO 4 solution (in 0.7 per cent. 

 NaCl solution) sufficed to do away with the irritability of the 



