8 Buchanan 



Controlled, however, by experiments made according to the first method, 

 there is no room for doubt as to what in the records represents the reflex 

 response of the muscle. Moreover, it ,gives evidence as to the reflex 

 response which is not obtainable by the first method alone. For a supra- 

 maximal stimulus is apt to produce in the record of the electrical response 

 of the gastrocnemius not one, but two, effects which are not there when the 

 stimulus is just maximal. The second such effect, instead of being much 

 smaller than the direct one and occurring some two-hundredths of a second 

 after it, is usually about equal to it in amount (as indicated by the steepness 

 of the rise in the curve), and occurs some six- to ten-thousandths of a second 

 after it. Two records of responses to supra-maximal stimuli in which this 



Fic. 2. — Fourth and seventh electrical responses of the 

 gastrocnemius of a normal preparation (Exp. 14) 

 obtained : 



' A, when the Intact sciatic nerve of the same side was exciteil 



by a supra-maximal stimulus. I'J'inie lines 770 per second.] 

 B, when the peripheral end of the same nerve, after divid- 

 ing it, was excited at the same place by a stimulus of the 

 same strength. [Time lines 780 per second.] 



effect is seen are reproduced in fig. 2. The upper curve represents the 

 fourth of four very similar responses obtained from a gastrocnemius when 

 its intact sciatic nerve was excited ; the lower one the third of three very 

 similar responses obtained from the same muscle excited at the same place 

 and in the same way, but after the division of the nerve above the place of 

 excitation. In both, and indeed in all the records obtained with this 

 muscle (except the very first, which was that of a response to a weaker 

 stimulus), the second effect, resembling the first direct effect, is seen. It 

 indicates, therefore, that, whether the nerve was in physiological connection 

 with the cord or not, the contact between the muscle and the proximal 

 electrode became again negative to the distal, and by about the same 

 amount as when the impulse first reached that spot along the motor nerve, 

 and, moreover, that it did so after an interval of 6a: In all the records 



