MEMBRANE CHANGES DURING STIMULATION 353 



like the organic anaesthetics or Mg salts appears to be 

 associated with a characteristic action on the proto- 

 plasmic surface-films; the latter are rendered more 

 stable, i.e., protected against the permeability-increasing 

 or disintegrative action of the pure salt solution; as 

 we have seen, a definite antitoxic influence is exerted 

 by these compounds when they are added in appropriate 

 concentrations to the pure salt solution. It is probable 

 that this stabilizing influence is responsible for the general 

 narcotizing properties of such compounds, since any 

 condition preventing alteration of the surface-films must 

 by that very action prevent stimulation, which is 

 dependent upon such alteration. 



The activating effect of pure alkali-salt solutions 

 upon the unfertilized eggs of marine animals is a phe- 

 nomenon which has many important physiological 

 affinities with stimulation, and is exhibited under 

 similar conditions. If starfish eggs are placed in pure 

 isotonic solution of NaCl (or similar salt) for five to ten 

 minutes (at 20°) and are then returned to sea water, a 

 considerable proportion form fertilization-membranes 

 and cleave, or even develop to a free-swimming stage. ^ 

 But the same solution to which CaCla has been added 

 (i mol. to 20 alkali salt) has little or no efTect.^ The 

 eggs of Arbacia are more resistant to this type of salt 

 action, and are only slightly affected by NaCl solution; 

 but pure isotonic solutions of more energetically acting 

 alkali salts, especially the iodides and thiocyanates of 

 Na and K, form fertilization-membranes and initiate the 

 activation-process in the same manner as other cytolytic 



^ American Journal of Physiology, XXVI (1910), 106. 

 ^Ibid.,XKVlI (191 1), 289. 



