OF VITAL PHENOMENA 129 



solutions of the chloride of an alkali metal the irritability dis- 

 appears least rapidly in NaCl and most rapidly in KC1 according 

 to the series: 



Na <Li <Cs <NH 4 <Rb <K 



If muscle remains in isotonic cane sugar solution the irritability 

 disappears but if they are returned to a salt solution the irritabil- 

 ity may be regained. According to Overton the cationic series 

 is about the same as the one above. According to C. Schwarz 

 the anionic series is: CNS <I <NO a <Br <C1 <CH 3 COO 

 <S0 4 , Tartrate <Citrate. 



If it is carbonic or sarcolactic acid inside the muscle fiber 

 that causes the polarization of the plasma membrane, this struc- 

 ture must be impermeable to all ions except H ions. The H ions 

 of the sugar may be of the same concentration as the H ions in- 

 side the fiber and thus abolish the polarization. If this is the 

 case, however, it is hard to see why the muscle is irritable in 

 a mixture of sugar and neutral salt unless the salt in some un- 

 known way changes the H ion dissociation of the sugar. The 

 sugar solution acts as an insulator and hence makes stronger 

 currents necessary for stimulation of the muscle directly. It 

 might also interfere with the transfer of the negative variation 

 from the nerve to the muscle by reducing the conductivity of the 

 solution immediately over the plasma membrane. I know of no 

 other suggestions that might explain the power of a cane sugar 

 solution in reducing the irritability of muscle. 



In this connection it may be of interest that the author found 

 it necessary to make the medium more acid than PH = 6.5 in 

 order to stop the pulsations of medusae or the heart of the Conch. 

 The action of ions on these pulsations was studied with a view 

 to determining the probability of the hypothesis of the antagonis- 

 tic action of ions in isotonic solutions. OH', Na' and K' stop 

 the conch heart in systole, whereas H, Mg" and Ca" stop it in 

 diastole. The first group tend to quicken and the second to re- 

 tard the rate. As observed by Ringer, Mayer and others, how- 

 ever, Ca" in the presence of other ions may tend to increase 

 the systolic phase of pulsations. We cannot pick out 9 pairs 

 of perfectly antagonistic ions, but the antagonism between Na : 

 and Mg"' is more perfect and between OH' and Ca" less perfect. 

 These antagonisms were more nearly perfect in the action of 



