CONDUCTIVITY 135 



the excitation, gradually decreases in the narcotized stretch as 

 the electrode is further removed from the point of entrance. 

 Beside a decrement of intensity, as the investigations of Frohlich 1 

 prove, the wave of excitation shows a decrement of the velocity 

 in the narcotized stretch. And it is probable that the wave of 

 excitation extends with progressive reduction in the velocity, 

 corresponding to the decrement of intensity. The work of Koike' 2 

 under the direction of Garten, in which the conclusion arrived at 

 is that the reduction in the velocity is the same throughout the 

 narcotized area, should not be accepted as conclusive in spite 

 of the delicate method employed. These investigations are ex- 

 tremely difficult, being in the field of the most delicate of present- 

 day methods. The decrement, which the wave of excitation 

 meets with in its progress in the narcotized stretch, makes the 

 conflicting testimony concerning the apparent separation of irri- 

 tability and conductivity intelligible. It depends entirely upon 

 the length of the narcotized area, and the amount of reduction 

 in irritability on the one hand, and the strength of the stimulus 

 used for testing the irritability on the other, whether the con- 

 ductivity will disappear before the irritability or vice versa. If 

 I test the irritability in the narcotized stretch with a weak stimu- 

 lus, just slightly above the threshold, then by slight reduction in 

 the irritability complete absence of response occurs, when the 

 same stimulus is applied. This occurs at a time when excitation 

 reaches the narcotized area from above and meets with a 

 decrement so slight that it can pass through the whole narcotized 

 stretch, that is, when the narcotized stretch is short enough. 

 If I test the irritability of the narcotized area with a strong 

 stimulus, far above that of the threshold, irritability will be 

 found to be present at a time when the conductivity for the exci- 

 tation, coming from above, is already obliterated. This is due 

 to the fact that the decrement in the narcotized area is already 

 great enough to bring about the complete disappearance of the 



IFrohlich: "Die Verringerung der Fortpflanzungsgeschwindigkeit der Nervenerre- 

 gung durch Narkose und Erstickung des Nerven." Zeitschrift allgem. Physiologic Bd. 

 Ill, 1904. 



2Izuo Koike: "Ueber die Fortleitung des Erregungsvorgangs in einer narko- 

 tisierten Nervenstrecke." Zeitsch. f. Biologic Bd. 5, 1910. 



