1913.] arising from Rivalry of Antagonistic Reflexes. 257 



though appearing with the other. A particular combination which works 

 need not necessarily work reversed, though it generally does so. 



As to what happens when the two rival stimuli are started together, the 

 observations have shown that sometimes then the reflex step starts at once 

 with full reciprocity of phase in the two muscles, and so proceeds co- 

 ordinately in that manner. Sometimes, however (fig. 14), the muscular effect 

 begins identically with contraction in the two muscles, and this is almost 

 immediately checked and reversed in one of the muscles so that that muscle 

 then begins, although a little late, to behave reciprocally in regard to its 

 fellow. In fig. 14 this correction takes place in time for L. muscle, although 

 starting wrongly, to have got into harmonious reciprocal step with its fellow 

 before even the completion of the first phase of the first step is reached 

 Harmonious reciprocity then continues. 



When the two rival stimuli are started together there seems a tendency for 

 the stronger to overcome the weaker altogether at first, and then to give way 

 to the latter a little later, and then later still to re-establish ascendancy, 

 again soon losing it, and so on. Thus a see-saw alternation of dominance 

 is arrived at. Observation 54 in fig. 13 exemplifies this. The weaker 

 stimulus (v. supra) 1. 17 there makes its effect felt as a deep inhibition 

 of a contraction already initiated by r. 14. And in the series of immediately 

 precedent observations 50 — 53, this effect of 1. 17 is seen to have each 

 time occurred with the same time -relations, although with successively 

 increasing effect. Evidence in the same direction is illustrated in fig. 7a. 



5. Influence of the Afferent Nerve of the Reacting Muscle. 

 The rhythmic effect of the antagonistic concurrent stimuli takes place when 

 the reacting muscle has been de-afferented. The presence of the proprioceptive 

 afferents of the muscle is therefore not necessary to the reaction. Fig. 15 

 shows the rhythmic stepping obtained from the right vastocrureus by con- 

 current stimulation of the antagonistic r. and 1. popliteal nerves. (The 

 signals in this experiment were set to mark upwards, not downwards as 

 in the other figures of this paper.) The observation begins with faradisa- 

 tion of r. nerve producing, after the initial spike {Anfangstetanus), 

 inhibition ; but the muscle being already relaxed, the preparation being 

 decapitate, the inhibition causes no visible further elongation of its 

 muscle, except the suppression of the initial contraction which it 

 itself had provoked. After 2'5 sees, the stimulation of the contralateral 

 popliteal is commenced, the stimulation of ipsilateral proceeding unaltered. 

 The result of concurrence of the stimuli is immediate rhythmic stepping of 

 the muscle. Four steps are taken during the continuance of the concurrent 



