204 PROTOPLASMIC ACTION AND NERVOUS ACTION 



characterizing group; e.g., two nitriles may be of very 

 unequal effectiveness — require different concentrations 

 to produce the same degree of depression, although 

 possessing the same polar group — and the same is true 

 of other compounds. In any series the depressant 

 action on oxidation is greater with the higher members 

 of the group; and the relative effectiveness of the 

 different compounds is closely similar to that observed 

 in experiments on narcosis. For example, the several 

 alcohols were found to lower the oxygen consumption 

 of birds' erythrocytes by about 50 per cent in solutions 

 of the following concentrations;^ Overton's determina- 

 tions of the minimal anaesthetizing concentrations of the 

 same compounds for tadpoles^ are cited for comparison: 



Concentration of Solutions Concentrations (Molecular) 



As an example of experiments with bacteria {Vibrio 

 Metschnikovii) the following series may be cited; to 

 diminish oxygen consumption by about half the following 

 concentrations of urethanes were required : 



Methyl urethane 0.67 m (5%) 



Ethyl 0.4111(3.5%) 



Propyl 0.097 m (1%) 



Isobutyl 0.043 m (o. 5%) 



Phenyl 0.003 ^^ (o-05%) 



^ Z. physiol. Chem., LXIX (1910), 452. 

 ^ Studien ilher die Narkose, p. loi. 



