1913.] arising from Rivalry of Antagonistic Reflexes. 259 



stimulation, i.e., in 4'5 sees. ; the ipsilateral stimulus is then withdrawn, and 

 under the influence of the remaining contralateral stimulus the muscle enters 

 at once into steady maintained contraction, and continues so contracted until 

 the stimulus is withdrawn. The muscle had been de-afferented October 7, 



1908, and was used for experiment nearly four months later, February 2, 



1909. In the experiments of Graham Brown* it has been shown that 

 stepping occurs after de-afferenting the muscles involved. 



6. Influence of a Component Stimulus subsequent to its Withdrawal. 



In the rhythmic reflex a contraction-phase (extension-phase of step) which 

 is in course of execution does not cease immediately on withdrawal of the 

 contralateral stimulus. On the contrary it continues its course for a brief 

 time and ends in smooth transition and reversal into relaxation. This want 

 of abruptness is strikingly different from the abruptness with which a reflex 

 inhibition excited by an ordinary stimulus against tonus often commences. 

 The excitatory phase thus continued after withdrawal of the contralateral 

 stimulus is frequently less ample than its predecessors where the stimulus 

 was not withdrawn (fig. 16, observation 2). A small final step to the series 

 is thus produced (fig. 1, observation 1). If the contralateral stimulus be 

 withdrawn during the course of the relaxation phase of the rhythmic reflex, 

 i.e. during the flexion phase of the step, often no subsequent contraction- 

 phase ensues (fig. 4, observations 3 and 4), even although the withdrawal 

 occur late in the course of the relaxation phase (fig. 4, observation 3). But 

 if the contralateral stimulus be relatively strong and the ipsilateral relatively 

 weak, and the former be withdrawn just before the end of the relaxation 

 phase, a small and somewhat delayed subsequent contraction phase may 

 ensue (fig. 10, observation 3), and even be followed by one still smaller and 

 still more delayed (fig. 1, observation 3). 



Conversely with the withdrawal of the ipsilateral stimulus. If this cease 

 during a relaxation phase that phase is completed more or less amply after 

 the stimulus withdrawal (fig. 4, observation 1). If it be withdrawn during a 

 contraction-phase no relaxation phase usually follows, but there may be just 

 the commencement of one if the ipsilateral stimulus is withdrawn at end of 

 a contraction phase (fig. 16, observation 1), and if the ipsilateral stimulus as 

 compared with contralateral be not too weak. 



* 'Roy. Soc. Proc.,' 1911, B, vol. 84, p. 308. 



