594 RALPH S. LILLIE 



tissues — appears to be the expression of this change in the phj^sieo- 

 chemical properties of the plasma-membranes. 



It was interesting to find that although anesthetics may thus 

 inhibit the cleavage-initiating action of neutral salts, they have 

 no appreciable influence on the similar action of the lipoid- 

 solvent fatty acids. This observation has an intimate bearing 

 on the general question of the mechanism of anesthetic action, 

 as well as on that of the nature of the process underlying the 

 initiation of cleavage. The fatty acid evidently acts by influenc- 

 ing the condition of the lipoids, and this effect is not prevented 

 by anesthetics; the salt-action, on the other hand, which pre- 

 sumably affects all of the colloids and particularly the proteins 

 of the membrane, is interfered with by these substances. It would 

 thus seem that the salt and the fatty acid may produce the same 

 effect by an action on different constituents of the plasma-mem- 

 brane. I shall discuss the possible unplications of this difference 

 in the relation of anesthetics to these two cleavage-initiating 

 agencies in the concluding section of this paper. 



EXPERIMENTAL 



Influence of anesthetics on the cleavage-initiating action of neutral 



salts (KCNS, Nal) 



The procedure in these experiments was essentially as follows. 

 The unfertiUzed Arbacia eggs were exposed for a brief period 

 (four or five minutes) to the pure isotonic solution of the salt used 

 (0.55 m KCNS or Nal), containing the anesthetic in known 

 concentration; they were then returned to sea- water. Eggs 

 treated in this manner with the pure salt-solution, free from 

 anesthetic, form fertilization-membranes and cleave as described 

 in my former paper; and if treated further with hypertonic sea- 

 water a large proportion form blastulae. But of those eggs 

 treated with the salt-solution containing a favorable anesthetic 

 in the appropriate concentration a considerable and sometimes 

 large proportion, varying with the anesthetic and time of ex- 

 posure, remain to all appearance quite unaffected, showing no 



