570 Prof. C. 8. Sherrington. On Reciprocal _— [Nov. 8, 
in intensity with much fineness by simply grading the intensity of stimulus 
applied to their respective afferent nerves.* 
It was sought, therefore, to find whether, when the relative intensity 
of the excitation of the two opposed reflexes is appropriately graded, there 
appears in the muscle a resultant action intermediate in degree between the 
relaxation which the inhibitory reflex acting by itself produces and the 
contraction which the excitatory reflex acting by itself produces. The accom- 
panying reproductions of graphic records taken in typical experiments give 
better than any verbal description the facts observed.t 
In the experiment furnishing fig. 2 the inhibitory afferent nerve 
(ipselateral peroneal) was faradised for the period marked by the upper 
signal. The secondary coil of the Berne inductorium was at 100 units 
on the Kronecker scale. The threshold stimulus for the inhibitory reflex 
lay at 40 units of the scale. It had been found that as the intensities of 
stimulus were increased from this threshold upward, the reflex inhibitions 
obviously increased in speed and persistence of effect, and also in the earlier 
range of the scale in depth relatively to duration of stimulus, but above 
about 5000 units there was no clear increase further; the inhibitions became 
maximal, The induced currents, when the electrodes were applied to the 
tongue-tip, were just perceptible at 1100 units on the scale. In the myogram, 
relaxation of the muscle is recorded by descent of the line, contraction by 
ascent. The effect of the stimulation of the inhibitory afferent nerve is seen 
to be a fairly rapid but somewhat hesitant descent of the myogram line. This 
hesitancy of relaxation is, in my experience, absent from strong inhibitions, 
and indicates here that the inhibitory reaction, though obvious enough, was 
not intense. When the inhibitory reflex had been in progress about 2 seconds, 
stimulation of the excitatory afferent nerve (contralateral popliteal) was 
commenced (shown by the lower signal line), the stimulation of the inhibitory 
afferent nerve continuing as before. The muscle at once contracted to a 
certain degree. The secondary coil faradising the excitatory afferent nerve 
was at 500 units on the Kronecker scale. The concurrent stimulation of 
both nerves continued for somewhat longer than 1 second; under it the 
contraction of the muscle persisted at about the same grade as that which it 
had almost immediately attained. The stimulation of the inhibitory afferent 
* Sherrington, ‘ Quart. Journ. of Expl. Physiol.,’ vol. 1, p. 98, 1908. 
+ The time line is above in all the figures and marks seconds. The signal lines marking 
the times of stimulation are below ; of them the upper marks stimulation of the inhibitory 
afferent nerve, the lower marking stimulation of the excitatory nerve. In all the 
myograph lever indicates lengthening of the muscle when it descends, and shortening of 
the muscle when it ascends. The further description of the figures is given in the text. 
t &. dbed., ‘Quart. Journ. of Expl. Physiol.,’ loc. cit. 
