THE REFRACTORY PERIOD AND FATIGUE 185 



Thorner^ the action current and not the muscle contraction served 

 as indicator. Here the fatigue of the medullated nerve brought 

 about by the deficiency of oxygen during prolonged stimulation 

 is demonstrated in the most obvious manner. (Figure 36.) 



Fig. 36. 

 Curve of action current of two nerves, one of wliiclj is stimu- 

 lated (plain line) whilst the other remains at rest (dotted 

 line). After decrease of irritability of the stimulated nerve 

 in nitrogen, oxygen is introduced into the chamber and 

 irrritability increases again. Then the previously resting 

 nerve b stimulated in nitrogen and the stimulated nerve 

 remains at rest (After Thomer.) 



Thorner^ further succeeded by a continuous stimulation of the 

 nerve in obtaining even in atmospheric air the indications of pri- 

 mary fatigue. The symptoms were exactly the same as those 

 characterizing fatigue of the muscle ; the extension of the course 

 of excitation and, as a consequence of this, the appearance of a 

 summation of excitation produced by tetanic currents and a re- 

 duction of irritability in response to single stimuli. The form of 

 the curve, resulting from alteration of irritability in fatigue and 

 recovery, likewise shows complete conformity with that of the 

 muscle. (Figure 37.) Finally Thomer^ proved that the nerve, 

 when fatigued by continuous tetanic stimulation in nitrogen, 

 could also partially recover in the latter if the stimulation was 



1 Th'orner: "Die Ermudung des markhaltigen Nerven." Zeitschr. f. allgem. Physi- 

 ologie Bd. VIII, 1908. 



2 Thomer: "Weitere Untersuchungen fiber die Ermudung des markhaltigen Nerven. 

 Die Ermudung in Luft und die scheinbare Erregbarkeitssteigerung." Zeitschr. f. 

 allgem. Physiologic Bd. X, 1910. 



3 TJwrner: "Weitere Untersuchungen fiber die Ermfidung des markhaltigen Nerven. 

 Die Ermfidung und Erholung unter Ausschluss von Sauerstoff." Zeitschr. f. allgem. 

 Physiologie Bd. X, 1910. 



