360 RALPH S. LILLIE. 



ing effects of environmental changes. There is a possibility 

 that the permeability to gases like carbon dioxide and oxygen is 

 also decreased, but this remains uncertain at present. 



It is important to note that changes in the resistance of plasma- 

 membranes, probably essentially similar to those underlying 

 anaesthesia, may occur under completely normal conditions, as 

 I have recently found in experiments on dividing sea-urchin eggs. 

 It had been shown earlier by Lyon, 1 Spaulding, 2 and Mathews 3 

 that during the normal cycle of cell-division these cells are much 

 more susceptible to poisons (cyanide, acids, ether, and K-salts) 

 at the time when the cleavage-furrow is forming, than in the 

 period preceding or following cleavage; during cleavage there is 

 also an increased output of CO?. 4 A rhythm of susceptibility to 

 poisons and of CO 2 -production is thus associated with the rhythm 

 of cleavage. This condition suggested the possibility that the 

 essential underlying condition of this rhythm might be a rhyth- 

 mical change in the properties of the plasma-membrane; and in 

 a series of experiments with dilute sea water it was found that 

 the eggs do in fact undergo cytolysis in hypotonic media far more 

 readily at the time when the furrow is forming than during the 

 intervals between cleavage. 5 In other words, the membrane is 

 relatively sensitive to osmotic disruption during cleavage, and 

 relatively resistant during the intervals between cleavage, i. e., 

 at the resting times when the cell is relatively highly resistant to 

 the action of poisons. This normal state of relatively high 

 stability may be compared to the condition which is imparted to 

 the membranes of irritable cells by anaesthetics. Increased 

 resistance to hypotonic solutions in the presence of anaesthetics 

 has been observed by Arrhenius and Bubanovic in blood cor- 

 puscles, as already cited. 



How does the anaesthetic produce this alteration in the prop- 

 erties of the membrane? Attempts to find parallels between the 

 effects of anaesthetics on living cells and on colloidal suspensions 

 of lipoids have not given entirely consistent results. Hober 



1 E. P. Lyon, Amer. Journ. Physiol., 1902, Vol. 7, p. 56. 



2 E. G. Spaulding, BIOL. BULL., 1904, Vol. 6, p. 224. 



3 A. P. Mathews, BIOL. BULL., 1906, Vol. n, p. 137. 



4 Lyon, Amer. Journ. Physiol., 1904, Vol. n, p. 52. 



'R. S. Lillie: Amer. Journ. Physiol., 1916, Vol. 40, p. 130. 



