
269 
On Reciprocal Innervation of Antagonistic Muscles.—Eighth Note. 
By C. S. SHERRINGTON, D.Sc., F.R.S, 
(Received April 17,—Read May 18, 1905.) 
(From the Physiology Laboratory, University of Liverpool.) 
The following note deals more especially with observations on inhibition 
occurring in instances of “reciprocal innervation” obtained as a spinal reflex 
reaction. My view is that inhibition of this kind is part and parcel of the 
normal reflex process, so that in a reflex it goes on side by side with excita- 
tion of other muscles opposed to those which are inhibited.* One main - 
consideration which supported the view is the correspondence of the skin- 
fields whence the reflex contraction of the one set of muscles and the 
inhibition of the opposed set of muscles can be elicited. So, also, the 
correspondence of the afferent nerve-trunks, and of the points of surface of 
the central nervous system whence are elicited the two effects. But to test 
the view further, I have now attempted to examine in some particulars the 
conditions attaching to the initiation, and the course run by the two phenomena 
under comparable circumstances. 
J. Even in one and the same spinal region the modes of origination, time- 
relations, etc., of the several types of reflex elicitable, ¢g.,in the dog’s hind 
limb, the “extensor thrust,” the “ direct-flexion reflex,” the “scratch reflex,” 
differ so greatly for each of the types as compared with the others, that in 
order to compare the inhibition phenomenon with the excitation phenomenon 
it 1s important to take both the phenomena from the same type-reflex. The 
type-reflex I have taken for the purpose has been the “ direct-flexion reflex” 
of the hind limb. 
- Each such type-reflex has features characteristic of it. A salient feature 
of this reflex chosen is flexion at the knee. For comparison of the inhibition 
and excitation respectively both hind limbs are taken and so prepared that in 
one leg only the knee flexors can act, in the other leg only the knee extensors. 
The stimuli to provoke the reflex are applied either to symmetrical skin- 
points or to symmetrical afferent nerves at, as far as practicable, symmetrical 
places in their course. For comparison the stimuli are made as far as possible 
equal on the two sides. This being arranged certain characteristic features of 
the reflex have been examined on the two sides respectively. 
(a) The “flexion reflex” has a “receptive skin-field” which though 
* *Roy. Soc. Proc.,’ vol. 52, p. 556, 1893. 
