ANTAGONISM BETWEEN SALTS AND ANESTHETICS 611 



CONCLUSIONS 



We reach thus the general result that the formation of fertiliza- 

 tion-membranes and the initiation of cleavage may be prevented 

 by anesthetics when the parthenogenetic agent is a neutral salt, 

 but not when it is a fatty acid. This contrast is what would be 

 expected on the assumption that the essential action of the 

 anesthetic is superficial, and consists in rendering the plasma- 

 membrane more resistant to alterations of permeability. Hence 

 the salt, which does not readily penetrate the unaltered egg and 

 produces its effect by increasing the permeability of the plasma- 

 membrane, is rendered less effective when the membrane has 

 been rendered relatively resistant or stabilized by the anesthetic. 

 The fatty acid, on the other hand, which penetrates the plasma- 

 membrane readily under all conditions, by virtue of its lipoid- 

 solubility, is not prevented in its action by anesthetics. 



Fatty acids and neutral salts represent two classes of agents, 

 one of which penetrates the egg-surface readily, the other with 

 difficulty and apparently only after increasing the permeability 

 of the plasma-membrane. Both induce parthenogenesis in a 

 typical manner. It is significant that of these two parthenoge- 

 netic agents one should be influenced in its action by anesthetics, 

 the other not. The fact that it is the more penetrating of the 

 two which is uninfluenced seems to indicate that the agent pro- 

 duces its essential effect by acting on some portion of the egg- 

 cytoplasm situated within the most external surface-layer, and 

 that calcium and anesthetics inhibit the action of salt-solutions 

 because they prevent the access of the salt to this critical region 

 of the egg. Otherwise it is difficult to understand why the anes- 

 thetic, which apparently stabilizes the surface-layer and hinders 

 alteration of permeability, is without influence on the action of 

 the fatty acid, although it inhibits the action of the salt. The en- 

 trance of the salt but not of the lipoid-soluble fatty acid would be 

 hindered by agents which act (like anesthetics and Ca salts) by 

 preserving s^mi-permeabihty unaltered, since semi-permeability 

 relates to lipoid-insoluble substances^ ^ only, as Overton first showed . 



^^ I.e., non-colloidal substances. Ruhland has shown that various dyes 

 which form colloidal solutions are exceptions to Overton's general rule. Cf. 

 Jahrb. wiss. Botanik, 1908, Bd. 46, p. 1. 



