VITAL PHENOMENA 143 



of protease with protein and a general diffusion and mixing of 

 the substances in the tissue. 



The cytolytic and antiseptic power of anesthetics varies with 

 their power of penetrating into the plasma membrane substance, 

 and hence varies approximately with their power of lowering 

 the surface tension of water. Solutions of the same surface 

 tension are called isocapillary solutions. It was found that iso- 

 capillary solutions of ether, alcohols, and acetone just caused 

 death of Fundulus eggs, with increase in permeability (McClen- 

 don, 1912 a). Czapek (1910) observed that indifferent anes- 

 thetics just caused death and increased permeability of plant 

 cells when they lowered the surface tension of water to .68. 

 Scheurlen (1896) observed' that NaCl increases the toxicity of 

 phenol. This may not be an additive effect, as NaCl may reduce 

 the surface tension of phenol solutions in the same way that it 

 reduces the surface tension of bile (Allen, G. D., 1915 a). 



It seems, therefore, that the toxicity of all indifferent anes- 

 thetics depends on the concentration and that the concentration 

 of the anesthetic in the plasma membrane is the only variable. 

 With other substances, however, this is not the case. If the 

 anesthetic is of such nature as to be chemically active in the 

 ordinary sense (not through residual valences) it is more toxic 

 than should be from the surface tension of its solution. Sub- 

 stances with basic, acid, reducing or oxidizing properties are 

 especially toxic, ammonia, phenol, formaldehyde and H 2 2 being 

 examples. But the acidity of phenol is not high enough to ac- 

 count for its toxicity, and formaldehyde, besides having a re- 

 ducing action, forms additive compounds with protoplasm in the 

 same way that it combines with ammonia to form hexamethylen- 

 tetramine. 



The toxicity of cations varies inversely with the electrolytic 

 solution tension, therefore the following series arranged in de- 

 creasing order of solution tensions is for the most part in in- 

 creasing order of toxicity : Cs, Li, Rb, K, Na, Ba, Sr, Ca, Mg, 

 Al, Mn, Zn, Cd, Sn, Fe, Tl, Co, Ni, Plb, (H), As, Cu, Bi, Sb, 

 Kg, Ag, PI, Pt, Ait. 



Mathews (1904 a) found the order of toxicity of salts of 

 these ions on Fundulus eggs to be Mn, Fe, Co, Ni, Zn, Pb, Cd, 

 Cu, Hg, Ag, Au. It may be noticed that Zn and Cd are out of 



