478 STUDIES IN GENERAL PHYSIOLOGY 



cases increase simultaneously with the valency. To say that 

 the toxicity increases in proportion to the increase in atomic 

 weight would be entirely wrong. The atomic weights are 

 9.08 for Be, 24.3 for Mg, 39.9 for Ca, 87.3 for Sr, and 136.9 

 for Ba. If the toxicity of the ions were proportional to 

 their atomic weights, this would show itself clearly in our 

 experiments. The velocities of migration correspond much 

 more perfectly with the relative toxicities of these ions. 

 According to Kohlrausch, the velocities of the ions at 18 

 are about as follows: |Mg = 42, |Ca = 49, |Ba = 53. Sr 

 is not given, but the velocity of its ion might stand close to 

 that of Ba. One sees that this series of velocities does not 

 show the jump which occurred in the former series from Na 

 to K, and which corresponded to a similar jump in the rela- 

 tive toxicities. The difference in the velocity of migration 

 of Mg and Ca is only 10 per cent., while that between the 

 corresponding members of the Li series, namely, Na and K, 

 is 50 per cent. We see also that no such jump exists from 

 the toxicity of Mg to that of Ca. The conclusion seems 

 justified, therefore, that the relative toxicities of the series 

 of ions Be, Mg, Ca, Sr, and Ba correspond more nearly to 

 the velocities of these ions than to their atomic weights. 



We have yet to discuss the toxicity of the anions. OH, 

 with its enormously high velocity of migration, is, as we have 

 seen, a relatively strong poison for muscle. On the other 

 hand, the Cl ion, with a speed of migration which is equal 

 to that of the K ion, is as harmless as the Li and Na ions, 

 as is shown by the behavior of the 0.7 per cent. Nad solu- 

 tion, which contains just as many Cl ions as Na ions. The 

 speed of migration of the NO 3 ion is, according to Kohl- 

 rausch, 60 at 18; that of SO 4 , 66; that of Cl, 62. The 

 fact that |H 2 SO 4 , HNO 3 , and HC1 show themselves to be 

 equally poisonous at the same concentration indicates that 

 in the concentrations which we employed the effect of the 



