46 



ILUNOIS BIOLOGICAL MONOGRAPHS 



[166 



IS THE TOXICITY OF A SUBSTANCE DUE TO OSMOTIC PRESSURE? 



A series of experiments was run with d-glucose (Table XXXVII) to deter- 

 mine the effect of osmotic pressure on the goldfish. When the molecular 

 concentration of the glucose is divided by two to make its osmotic pressure 

 comparable to that of a normal salt solution, it is seen that the toxicity 

 of the glucose is still below that of the particular salt to which it is com- 

 pared. This difference is even more striking when the fact that the salts 

 are not completely ionized is taken into consideration and that this is 

 more than sufficient to allow for complete ionization of salts of bi and tri 

 valent acids and bases. The improbability that the toxicity of a substance is 

 due to osmotic pressiu-e is further emphasized by the fact that the toxic activi- 



TABLE XXXVII 



d-Glucose. Temperature 21.5°C. 



ties of substances like potassium cyanide, hydrochloric acid, the alcohols, 

 caffeine, phenol, and pyridine are not in proportion to their molecular concen- 

 trations. 



THEORY OF THE POISONING EFFECT ON TOXIC SUBSTANCES 



Osterhout (1915) has shown in a very interesting paper that death in the 

 Laminaria, when placed in NaCl solution of the same conductivity as that of 

 sea-water, as measured by the fall of electrical resistance, does not follow a 

 straight line when electrical resistance is plotted as ordinate and time as 

 abscissa, but foUows a curve which, he points out, "follows the course of a 

 monomolecular reaction. " 



The effect of poison on protoplasm might be compared to a system of 

 chemical reactions which finally result in the death of the organism. It has 

 been shown outside the living organism that KCN retards oxidation. Kastle 



