THE PHYSIOLOGY OF CELL DIVISION 29 



simple membrane-formation, and thus enable a larger propor- 

 tion of eggs to recover the normal state and proceed with their 

 development. 



During the summer of 1912 at Woods Hole I have experimented 

 from this point of view with solutions of various anesthetics. 

 Substances of this class have been found to check the permea- 

 bility-increasing action of pure isotonic solutions of sodium and 

 potassium salts on sea-urchin and starfish eggs. These anti- 

 cytolytic effects are seen in certain definite concentrations, which 

 correspond closely with those which anesthetize the neuromus- 

 cular system of marine organisms Uke Arenicola larvae; in these 

 concentrations anesthetics have the general effect of rendering 

 the plasma membranes of cells — egg-cells, muscle cells, pigment 

 cells, as well as structures like cilia — more resistant than normally 

 to agencies which tend to increase permeability (or cause break- 

 down in the case of cilia). ^® Anesthetics thus counteract the 

 action of penneability-increasing agencies, and it is probably for 

 this reason that they prevent stimulation (which involves tem- 

 porary increase of permeability) as well as retard cytolysis. In 

 some cases they have been definitely shown to decrease the nor- 

 mal permeability of the plasma-membranes.^^ The alterations 

 which they induce in the properties of the membranes are thus, 

 generally speaking, opposite in kind to those caused by permea- 

 bility-increasing or cytolytic agencies. We should thus expect 

 that if, as above assumed, the plasma membrane of the egg is 

 deprived of its normal semi-permeability by the membrane- 

 forming process — and is thus brought into a state which event- 

 ually leads to cytolysis — an after-treatment with anesthetics will 

 tend to restore the original semi-permeabihty and will thus ren- 

 der the condition of the egg more favorable to the continuance of 

 development. Solutions of anesthetics, in other words, ought to 

 produce effects similar to those of hypertonic sea-water or cyanide. 



1^ Cf . my recent papers in the American Journal of Physiology on antagonisms 

 between salts and anesthetics: 1912, vol. 29, p. 372; vol. 30, p. 1; 1913, vol. 31, p. 

 255. 



^^ Cf. the recent experiments of Osterhout, Science, 1913, N. S., vol. 37, p. Ill; 

 also my observations on Arenicola larvae; American Journal of Physiology, 1909, 

 vol. 24, pp. 25 seq. 



