EXAMINATION OF SOME SPINAL NERVES 151 
in the Frog, I have in a number of experiments found the exhibition of strychnia still produce 
spasms, when the possibility of asphyxial complication has been avoided, after all the afferent roots 
belonging to the whole length of the isolated spinal cord below transection had in the Cat and 
Dog been cut through, and when it has been proved by subsequent dissection that not a single 
afferent root filament had been left.* This result is obtained even when a period of six to seven 
hours is allowed for subsidence of the current of injury in the severed nerve-fibres of the afferent 
roots. I think, therefore, these experiments prove that strychnia acting upon a portion of 
Mammalian spinal cord that has been severed from the brain, can excite the motor neurons in it 
either directly or induces in them some autochthonous excitation. That this mode of excitation 
does not discriminate between these functional groups of neurons in the same manner as excitation 
of the posterior roots, is interesting, but not opposed to the above view. On local reflex action the 
activity of the flexors at knee and elbow predominate over the extensors. Conversely in strychnia 
spasm the extensors predominate. In most local spinal reflexes, as I pointed out some time since,t 
only one set of an antagonistic muscle-couple contract ; in strychnia spasm, when severe, both sets 
usually contract synchronously. 
In the same way, asphyxia, especially when produced rapidly, evokes discharge of the 
motor neurons of the cord, and the discharge produced by it is of both extensors and flexors, and 
occurs as readily when all the afferent roots of the limb have been severed as when the afferent 
roots remain intact. The chemical excitation of the asphyxial condition so far resembles that of 
strychnia that in contradiction to the tonic conditions under discussion here, it is due to an 
excitation not conveyed via the afferent roots, but must be autochthonous in the grey matter of the 
cord. I do not mean to infer that these two modes of chemical excitation act entirely similarly, 
and, indeed, there is obviously a predilection in the case of strychnia for the motor cells of the 
somatic muscles, in the case of the asphyxial condition for the visceral muscles { e.g., the arrectores 
pilorum), or rather for the spinal motor neurons of the sympathetic ; I mean, merely, that both 
stand out together in strong contrast with such a condition as decerebrate rigidity following removal 
of the cerebral hemispheres, for in this last the contraction of the extensors of elbow and knee 
can be almost immediately reduced or abolished by severance of the afferent roots of the spinal region. 
Again, extensors of the knee appear more readily excited from the cortex after severance of 
the lumbo-sacral afferent roots. In our experiments on the influence of the sensory roots of the 
limbs on the co-ordination of their movement. Dr. Mott and myself notedj that, in the 
co-ordination produced, proneness to extension of the knee played a part. Dr. Mott allows me 
to mention this, and it will be dealt with more fully in our complete paper, still to be published. 
* In saying the above I do not intend to controvert the likelihood that under ordinary circumstances the convulsions of 
strychnia-poisoning are largely of reflex origin. H. E. Hering has thoroughly shown that strychnia convulsions are set in 
abeyance by severance of the afferent nerve-roots. In my experiments large doses were given, and the object of the experiments 
was to decide whether, in the absence of sensory paths and without the concurrence of asphyxia — which latter of itself can 
produce autochthonous convulsions — strychnia can still produce spinal convulsions in Mammals : it does. loth July, 
■ 1897.— c.s.s. 
\ ' Journ. of Physiol.,' vol. 13, p. 621, &c., 1892. J ' Proc. Roy. Soc.,' vol. 57, 1895. 
