1905.] On Reciprocal Innervation of Antagonistic Muscles. 271 
”) 6 
(ce) The “ flexion reflex,” unlike “extensor thrust,” “pinna reflex,” etc., can 
be well evoked in my experience by make or break of a galvanic current. 
This make or break reflex is shown in the “extensor” preparation by inhibi- 
tion, just as it is shown in the “ flexor” preparation by contraction. With 
suitable strength of stimulus the break of a descending current is more effective 
for the reflex inhibition than the make, and vice versd for an ascending 
current, just as with contraction. The “flexion reflex” can also to a much 
greater extent than can the scratch reflex be maintained by passage of the 
constant current. In this respect it resembles the vasomotor and respiratory 
reflexes examined by Griitzner* and by Langendorff and Oldag,+ and also the 
sensual reaction which similar stimulation excites in ourselves—a point of 
interest when the connection between nociceptive reflexes and dolorous sensation 
is remembered. When the constant current is thus applied to the limb in 
which the extensors have been prepared, inhibition proceeds in them as does 
contraction in the flexors when that current is similarly applied to the limb 
in which the flexors have been prepared. 
(€) The latent time of the “ flexion reflex” is throughout my experience 
shorter than that of some other reflexes of the limb, notably than that of the 
“scratch reflex.” This feature is revealed in the inhibition of the extensors 
just as in the contraction of the flexors. Great differences of latency in the 
“flexion reflex” as in other reflexes can be obtained by, apart from variance 
‘in intrinsic condition of the reflex preparation, variance in the external 
stimuli in intensity, suddenness, frequency of repetition, etc. The effect of 
such variations is the same in kind, and, in my experience, in extent, when 
tested by the reflex inhibition as when tested by the reflex contraction. Thus 
with strong stimuli I have found as short a latency as 32 o for the inhibition, 
which is slightly shorter than the shortest for contraction under like circum- 
stances that I have yet met with. With weak stimuli I have occasionally 
met with a latency as long as 400 o for each effect. 
(n) A good criterion of comparison between the reflex inhibition and the 
reflex contraction in the “ flexion reflex” under excitation by an intermittent 
stimulus is the number of stimuli summed for initiation of the reflex as 
exhibited on the one hand in contraction of the flexors, on the other hand in 
relaxation of the extensors. The number of successive single stimuli summed 
for the initiation is less as their individual intensity is greater.{ 
When the summation is compared, in the same reflex preparation, in the 
reflex exhibited as inhibition (relaxation) in the knee extensors of one limb 
* ‘Pfliiger’s Archiv,’ vol. 17, p. 238, 1878. 
+ Ibid., vol. 59, p. 206, 1894. 
t W. Stirling, ‘Arbeiten a. d. Physiol. Anstalt z. Leipzig,’ 1874, p. 239. 
