64 Prof. C. 8. Sherrington. On Reciprocal [ Nov. 4, 
The contraction of the after-phase is extremely easily and rapidly cut short 
by a repetition of the stimuius upon which it followed. That stimulus 
inflicts on it with speed and certainty an inhibitory relaxation (figs. 7 and 8, 
A and B). Even the briefest repetition of the stimulus suffices. I have 
seen a repetition lasting only one-twentieth of a second cut itdown. In fig.7 
is seen the effect of renewal of the stimulus for one-tenth of a second 
(fig. 7, third application of stimulus). The stimulus cuts it down by 
inhibitory relaxation, much as it cuts down a crossed extensicn reflex.* 
On repetition of the original stimulus, the contraction of the contraction- 
phase is lessened or suppressed according to. the intensity of the stimulus 
or the duration of its reapplication. On cessation of the reapplication the 
contraction-phase sets in again (figs. 7 and 8, A, B); subject only to the 
general conditions already mentioned as governing the contraction and to 
the condition that the reapplication has not been strongly repeated many 
times. Thecontraction-phase tires out more quickly than does the inhibition- 
phase. The contraction-phase that appears after a repetition of the stimulus 
does not seem tc be simply a continuation or reappearance of the old con- 
traction-phase that had been inhibited, for it often exceeds in intensity the 
intensity which the foregoing contraction-phase had at the moment when 
the inhibitory stimulus was renewed (fig. 7, second stimulation; and fig. 8, B). 
Nevertheless, the new contraction-phase has not so great intensity as 
the previous contraction-phase showed at outset (figs. 7 and 8, A). The 
fresh contraction-phase following each repetition of the inhibitory stimulus 
is on the whole somewhat less than the one preceding it (figs. 7 and 8, A, B), 
and the series of contraction-phases show progressive decline (figs. 7 and 8, 
A, B). Fig. 8, A, B, exhibits the first four and the last two of a series of 
15 diphasic “ flexion-reflexes ” provoked in the extensor muscle (vasto-crureus) 
without pause between them. The external stimulus was not intense, and 
its intensity remained the same throughout this series, although the duration 
of its several applications was not exactly the same for each member of 
the series, since the short-circuiting key opened and shut by hand instead 
of automatically. The contraction-phase dwindled progressively in its 
repetitions, and on (fig. 8, B) withdrawal of the sixteenth stimulus no con- 
traction-phase followed. The faradic stimulus was then (fig. 8, B) repeated 
with increased intensity, although with somewhat shorter duration. On 
cessation of this (seventeenth) stimulation, although little or no further 
lengthening of the already fairly-relaxed muscle had been obvious during 
the stimulation, a contraction-phase of considerable intensity at once 
followed (fig. 8, B). On repetition of the stimulus this was at once cut 
* See fig. 3, in eighth Note of this series, ‘ Roy. Soc. Proc.,’ B, vol. 76, p. 277. 
