1893.] Correlation of Action of Antagonistic Muscles. 411 



rectus, because of the simplicity of its antagonistic coupling with the 

 internal rectus. But the external rectus it is not easy without dis- 

 turbance of other parts to isolate sufficiently to feel certain that 

 tension put upon it remains confined to it alone. I adopted, therefore, 

 for examining the antagonism of the external and internal recti the 

 method of paralysing one and then examining the activities of the 

 other. When examining in the Monkey the movements of the digits 

 obtainable by cortical excitation, if movement, e.g., flexion, of the 

 hallux or pollex is elicited, and the nerve to the flexors of the digit 

 be then severed, renewed cortical excitation at the same spot still 

 produces a movement ;* this movement is generally in direction the 

 reverse of that previously obtained; this "reversal" is, however, not 

 invariably obtained; occasionally there results a feeble movement in 

 the same direction as the movement previously obtained. In three 

 experiments this movement has been so decided as to lead one to re- 

 examine carefully the site of division of the peripheral nerve in order 

 to assure oneself that it had been really severed completely. The 

 persistence of movement in the same direction as before the flexor 

 nerves are severed must indicate that the stimulation applied to the 

 cortex produces at each repetition an inhibition of the tonus of the 

 muscles antagonistic to the flexors, that is to say, of the extensor 

 muscles. My experience of this inhibition is that it cannot, even 

 when it occurs, be demonstrated many times in succession. The 

 phenomenon of reversal is, on the other hand, obtained repeatedly 

 with facility. 



A power to inhibit the activity of striated muscle has, therefore, to 

 be included among the attributes of the " motor " cortex of the 

 hemisphere. In the coordination of the movements of the eyeballs it 

 appears to play an important and easily demonstrable part. Ferrierf 

 discovered that excitation of a particular portion of this cortex pro- 

 duces a conjugate movement of both eyeballs in a direction away 

 from the hemisphere in which the stimulation is employed. If the 

 appropriate area of the cortex of the left hemisphere be excited the 

 movement is of both eyeballs to the right. My enquiry regarding 

 the correlation of action of the antagonistic internal and external 

 recti in this movement may be stated as three questions. Is the 

 movement carried ont : 



a. By contraction of the left internal rectus and the right external 

 rectus, their antagonist muscles undergoing the while simply passive 

 traction ; 



fi. By contraction of the above two muscles combined with slighter 

 contraction (steadying) of their antagonistic muscles (left external 

 rectus and right internal rectus) ; or 



* Sherrington, 4 Journ. of Physiol.,' vol. 13, p. 671, &c. 

 t Ferrier, ' Functions of the Brain,' London, 1876. 



2 G 2 



