
1905.| On Reciprocal Innervation of Antagonistic Muscles. 291 
reflex inhibition of the extensor muscles, normally obtainable from the 
internal saphenous nerve, but that obtainable from the peroneal and popliteal 
nerves, and from the hamstring nerve, remains unreversed, though the 
strength of the inhibitory effect of these nerves may be very distinctly less 
than normal. Later, as the condition progresses, the inhibitory effect 
normally belonging to the peroneal and popliteal nerves becomes actually 
reversed into excitation. Finally, even that of the hamstring nerve itself 
is reversed. This is the same sequence of effect pursued by progressive 
increase of dosage of strychnine. 
One difference that seems apparent between the action of the tetanus-toxin 
and the strychnine in these observations is that in the relatively slow 
progress of the tetanus it is easy to note a stage in which the conversion 
of the inhibition effect into excitation effect has occurred, while there is 
yet none of that obvious lowering of the threshold of reflex reaction which 
early marks the course of strychnine poisoning, and has been drawn attention 
to by many observers. 
In experiments on the hind limb, I have usually introduced the toxin 
into the sciatic trunk well below the hamstring branch, more rarely into the 
hamstring nerve as well, or alone. I have found the inhibitory effect of 
the internal saphenous nerve (stimulated in its course below the knee) 
converted to excitation in 48 hours from the time of inoculation. In the 
gradual progress of the condition, I have several times found the hamstring 
nerve produce slight inhibition of the extensor if the initial posture taken 
at the knee be extension, and yet produce distinct excitation of the extensor 
if the initial posture taken at the knee be flexion. This is in accord with 
evidence insisted on in the sixth Note.* 
It is noteworthy that the nerve, namely, the internal saphenous, which, 
in the lower limb, thus early shows the typical. effect, 2.¢., conversion of 
inhibition to excitation, lies remote from and without peripheral connection 
with the nerve trunk which has been the seat of inoculation. In the same 
way, before the condition has spread so as to cause obvious symptoms in 
the opposite as well as in the inoculated limb, the reflex effect of stimulation 
of the central end of the hamstring nerve of the inoculated limb can be 
seen to be at the opposite knee slight inhibition of the extensors—that is, 
in my experience, the normal effect, 2.e., obtains in the unpoisoned state. 
But the reflex crossed effect from the corresponding nerve of the non- 
inoculated limb can be seen to be not inhibition, as it normally should be, 
but excitation. In this case, again, inhibition effect has been changed to 
excitation effect, and this time in a crossed reflex, and the change is 
* © Roy. Soc. Proc.,’ vol. 66, 1900. 
