476 STUDIES IN GENERAL PHYSIOLOGY 



atomic weights. On the other hand, we notice a beautiful 

 agreement between the relative toxicity of the individual 

 members of this group and the velocity of the migration of 

 the ions. According to Kohlrausch, the speed of migration 

 of the Li ion at 18 is 33, that of the Na ion 41, that of the 

 K ion 60. The velocities of the ions of Rb and Cs are equal 

 to the velocity of K, according to Ostwald. A great jump, 

 therefore, occurs from Na to K in the velocity of the migra- 

 tion of the ions, while no such jump occurs from K to Eb 

 and to Cs, just as is the case in their toxicity. It may 

 therefore be said that the relative toxicity for muscle of the 

 ions of this group is rather a function of their velocity of 

 migration than of their atomic weight. The heavier ele- 

 ments are, therefore, more poisonous only because their ions 

 have a greater speed of migration than the Na and Li ions. 



On the other hand, the toxicity of K ions is much less 

 than that of the hydroxyl ions. In our experiments with 

 alkalies the addition of 10 c.c. of a one-tenth normal alkali 

 solution to 100 c.c. of a physiological NaCl solution was 

 sufficient to bring about a decided decrease in irritability. 

 It did not matter, however, whether the alkali used was 

 KOH, NaOH, or LiOH. At this concentration only the OH 

 ions were poisonous, while the toxicity of the K ions did not 

 appear. 



The investigation of the relative toxicity of the bivalent 

 ions Be, Mg, Ca, Sr, and Ba is rendered difficult by the fact 

 that a solution of the chlorides of these elements of the 

 same concentration as a 0.7 per cent. NaCl solution has a 

 greater osmotic pressure than the sodium-chloride solution. 

 The muscle, therefore, loses water (as we have seen) in such 

 a solution, and the loss in water must also decrease the irri- 

 tability. We are, however, in a position to estimate the 

 influence of the loss of water on the irritability. The loss 

 of water in these solutions was about equal to that in a 1.05 



