1908. | Innervation of Antagonistic Muscles. 577 
disappearance of its contraction, documenting further the presence of inhibitory 
action under the stimulation, weak as it is, of the inhibitory afferent nerve. 
Finally, the stimulation of the inhibitory afferent nerve is withdrawn, and 
there then ensues a slight rebound contraction (successive induction*), With 
the result of the combined stimulation obtained in. this case, there must be 
compared the result obtained a few minutes later (fig. 5, A) under similar 
conditions, save for reversal of the sequence of the stimulations. In fig. 5, A, 
the same weak stimulation of the inhibitory afferent nerve (upper signal line) 
opens the experiment; the slow hesitating relaxation of the muscle evidences 
the feeble intensity of the inhibitory influence. After this has been in 
progress for some four seconds, stimulation of the excitatory afferent nerve 
is commenced. The muscle at once contracts and in the next four seconds 
attains almost the summit of its’ contraction elicitable by the combined 
stimulation. That this grade of contraction is, however, less than what it 
would exhibit under stimulation of the excitatory afferent nerve alone is clear 
from what happens when the weak stimulation of the inhibitory afferent 
nerve is discontinued. On removal of this inhibiting stimulus the myogram 
line immediately ascends and a higher grade of contraction is uniformly main- 
tained for the following three seconds, at end of which time stimulation is finally 
withdrawn from the excitatory afferent nerve. The muscle then relaxes, but 
with characteristically slower lengthening than in fig. 5, B, where the weak 
inhibitory stimulus was still in play at the time of withdrawal of the stimula- 
tion of the excitatory afferent nerve. 
Finally a point already raised may be returned to for fuller exemplification. 
The records furnishing figs. 5, 3, 2, and 4 have all been chosen from a series 
of observations obtained in near succession and from the same preparation. 
The intensity of the stimulus applied to the excitatory afferent nerve 
remained the same throughout them all, namely, 500 units on the Kronecker 
scale. On the other hand, the intensity of the stimulus applied to the 
inhibitory afferent nerve was different in the four observations figured ; 
in fig. 5 it was 50 units of the Kronecker scale; in fig. 3, 75 units ; in fig. 2, 
100 units; and in fig. 4 it was 150 units. On comparing together in the 
four figures 5, A, 3, 2, and 4, A the levels assumed by contraction under 
the combined stimulation in each case, and the relation of those levels to 
the depth of relaxation under inhibitory stimulus alone, and to the height 
of contraction under excitatory stimulus alone, it is clearly seen that the 
four levels form a graded series, and that the grading accords with the 
relative intensities of the stimuli. The length of the muscle under 
the combined stimulus, Excit.+Inhib., more resembles the lefigth under 
* ‘Roy. Soc. Proc.,’ vols, 76 and 77, 1906. 
VOL, LXXX.— bh, 22 
