MUSCULAR TWITCHINGS 751 



beat in a pure BaCl 2 solution. It goes without saying that 

 in pure solutions of MgCl 2 , CaCl 2 , and SrCl 2 a muscle does 

 not show any rhythmical contraction. In a ~ BaCl 2 solu- 

 tion, however, the muscle beat for forty minutes; in a ^ 

 solution, for one and a half hours; in a ^ BaCl 2 solution, 

 for over an hour; and in a ^ BaCl 3 solution, for about 

 half an hour. The beats showed the same tetanic form char- 

 acteristic of the presence of barium. The fact that the beats 

 stop sooner in a f^ BaCl 2 solution than in a ^ solution 

 is due to the poisonous effects of barium. The fact that the 

 beats stop also very soon in a ^ BaCl s solution is due to 

 the enormous absorption of water which occurs in such weak 

 solutions. 1 



Similar facts were found for Ba(NO 3 ) 3 and Ba (HO) S . 

 The most striking fact is that the stimulating power of Ba 

 salts is greater than that of the corresponding Na salts. 

 In a -gf BaCl 3 solution the muscle may begin to beat in a 

 few minutes and may continue to do so for half an hour. I 

 have even occasionally noticed rhythmical contractions in a 

 y^ Bad 2 solution. But I have never noticed any rhyth- 

 mical contractions of muscle in a ^ NaCl solution, and as 

 a rule even in a ^ NaCl solution the twitchings begin only 

 after a long latent period and last but a short time. 



Barium is, however, not the only bivalent kation whose 

 chloride possesses a higher stimulating power than that of 

 the chloride of univalent kations. It was found that the 

 chlorides of the heavy metals are also capable of producing 

 rhythmical twitchings or beats of muscles in much lower 

 concentrations than those found effective in the case of NaCl 

 or LiCl. In T ^ 7 solutions of ZnCl 2 strong beats occurred, 

 which, however, did not last long on account of the rapid 

 imbibition of the muscle with water, as well as on account 



i The beats in Ha< ' 1 . solution often do not begin at once, but after a latent period 

 of from two to fifteen minutes. 



