196 



Tait and Gunii 



responses tend to fall off in heiglit with repetition of the successive series 

 of stimulations. Thus in %. 1, tracing (2), it is very clear that the 

 responses to the first six series of stimulations become progressively lower 

 and lower. This eflfect may be due either to rapidly deepening anaesthesia 

 of the nerve or to fatigue. That it is due to some fatigue condition 

 and not to progressive and rapid aneesthesia, is indicated by the fact that 



Fig. 2 (reduced to about one-half).— Length of nerve anaesthetised, 3 cm. Duration of application 

 of yohimbine, 40 minutes. Rate of stimulation, 144 per sec. Rate of drum, 1'5 mm. per 

 sec!^ Six series of responses are shown, corresponding to intensities varying from 30 to 500 

 Kronecker units. 

 Note (i.) the tetani are all of the "fatigue " form ; (li.) the responses corresponding to strong stimulation are more 

 marked than those corresponding to weak ; (iii.) in any given series with constant intensity of stimulation 

 the height of the responses varies as the duration of the period of rest between stimulations. 



if longer intervals of rest are allowed between the successive sets of 

 excitations, the effect does not occur. Further, the effect is most marked 

 when the intervals of rest between successive series of stimulations are 

 made progressively less and less, as is the case in the first six responses of 

 fig. 1, tracing (2), or in the middle series of responses in fig. 3. 



