13-i 



IRRITABILITY 



of excitation is obliterated. This important fact has been fur- 

 ther estabHshed by the experiments of Boruttau and Frdhlich^ 

 in which they studied the intensity of the current of action, 



Fig. 22. 

 Scheme of the decrement of the excitation wave In the narcotized stretch of a 

 nerve. A— The narcotized stretch (indicated by the cross section of the 

 chamber) is 30 mm. long. The ordinates of the dotted lines indicate the 

 amount of the decrement. If the decrement is sHght (upper dotted line), the 

 excitation wave passes the narcotized stretch and increases again on entering 

 the normal stretch. If the decrement is great (lower dotted line), the excita- 

 tion wave is obliterated towards the end of the narcotized stretch and the 

 muscle remains at rest B— The narcotized stretch is 15 mm. long. The 

 decrement is slight The excitation wave can therefore pass into the normal 

 stretch and here increase again. C— The narcotized stretch is 15 mm. long. 

 The decrement Is great The excitation wave is obliterated, therefore, in the 

 narcotized stretch, and the muscle remains at rest 



produced by a wave of excitation, from two points in the narco- 

 tized stretch. The wave of negative variation, brought about by 



\ Boruttau und Frdklich: "Erregbarkeit und Leitfahigkeit des Nerven." Zeitschrift 

 f. allgem. Physiologie Bd. IV, 1904. The same: "Electropathologische Untersuchungen 

 ueber die Veranderungen der Erregungswelle durch Schadigung des Nerven." Pfliigers 

 Arch. Bd. 105, 1904. 



