
1905.] On Reciprocal Innervation of Antagonistic Muscles. 289 
in the spinal cord in these instances the process of inhibition—whatever that 
may essentially be—into the process of excitation—whatever that may 
essentially be. The nexus was pre-existent, but the effect across it was 
signalised by a different sign—minus prior to the strychnine or tetanus toxin, 
instead of plus, as afterward. 
The observed difference between the facility with which strychnine converts 
the inhibition by the hamstring nerve into excitation, and that with which 
it converts the inhibition of the other limb-nerves mentioned, does not seem 
referable to a different action on muscular afferents and cutaneous afferents 
respectively. Stimulation of the central end of the purely muscular nerve to 
the vastt and crureus evokes normally inhibition of the hamstrings of the 
opposite limb, but under strychnine it evokes their contraction. In that 
case, therefore, the strychnine converts with facility the inhibition by a 
muscular afferent into excitation, just as with the skin nerves mentioned. 
If strychnine can convert a central inhibition into an excitation, and if the 
various normal reflex spinal inhibitions show differences, one from another, 
in the ease with which their mechanisms undergo conversion into excitatory 
mechanisms by strychnine, the synchronous excitation of antagonistic muscles 
in certain willed actions becomes, perhaps, less difficult to understand. Vaso- 
depressor reflexes under chloral (v. Cyon), chloroform (Bayliss), etc., change 
into vaso-constrictor under curare, morphia, etc. But the reversal does not 
appear to occur with equal facility in all afferent nerves alike. It is stated 
to be impossible to obtain any vascular reflex but a depressant one from the 
“depressor” nerve. This nerve, arising in the heart (v. Cyon)* and aorta 
(G. Koster and A. Tschermak),+ may in a sense be considered the afferent 
nerve of the muscle antagonistic to the ring-musculature of the arteries, 
namely, the muscle whose tonus it reflexly depresses. It is in that way 
comparable with the afferent nerve of the hamstring muscles in relation to 
the extensors of the knee. The depressor action of the hamstring nerve on 
the knee-extensor seems, as just said, in my experience, particularly resistant 
to conversion from inhibition into excitation by strychnine. 
The conversion of spinal inhibition into excitation by strychnine explains 
the simultaneous contraction of large inharmonious groups of muscles in 
strychnine convulsions. It also explains the occurrence, under a given 
stimulus, of reflex contraction of muscles that previously do not seem, under 
superficial examination, to be reached by the reaction. These muscles are 
really included in the reflex effect normally, but the effect on them then being 
imhibition, it passes unnoticed, unless special means are adopted for seeing it. 
* “Ludwig’s Arbeiten,’ Leipzig, 1866, p. 128. 
t ‘ Pfliiger’s Archiv,’ vol. 93, p. 24, 1902. 
