1893.] Correlation of Action of Antagonistic Muscles. 419 



was strong divergence of the optic axes in the vertical plane, with the 

 right pupil depressed, the left pupil elevated sometimes considerably. 

 The same held true in the results of excitation of the occipital regions 

 of the cortex, and the left eye generally commenced movement under 

 excitation of the right occipital cortex distinctly earlier than did the 

 right eye, just as when the 6th nerve alone had been divided ; so that 

 under excitation of the right occipital cortex there was usually at one 

 phase of the movement instead of any convergence of the optic axes 

 a strong divergence of them. 



It was noticeable that after division of the 6th nerve, either alone 

 or in conjunction with the 4th, also in one experiment in conjunc- 

 tion with the 5th, the pupil of the eye on the same side as the nerve 

 section was slightly but distinctly larger than in the opposite eye. 

 This observation led me to stimulate the 6th root in the Monkey, but, 

 although the eye was in result moved outwards, I could not satisfy 

 myself that any constriction of pupil at all occurred, although the 

 pupil was well dilated at the time. In the case of the internal 

 straight muscle, I believed it would be less easy to sever its antago- 

 nist's nerve than in the case of the antagonist of the external rectus. 

 I therefore made several earlier experiments, employing section of 

 the external rectus and its nerve inside the orbit. The above de- 

 scription is, however, not based on the results of those earlier experi- 

 ments in which the orbit was opened, because : (1) It was found then 

 impossible to be quite certain that some remnant of movement or drag 

 in the muscle could not affect the globus sufficiently to simulate the 

 movement that might result from a relaxation of the antagonistic 

 muscle ; (2) because when once the orbit has been opened, or its 

 contents dissected, the movements of the globus are deranged suffi- 

 ciently to beset with doubt any interpretation that can be put upon 

 them ; (3) finally, because destruction of the muscles or their nerves 

 in the orbit or cavernous sinus involves destruction also of concomi- 

 tant sensory fibres from the 5th nerve which may exert a consider- 

 able influence on the antagonistic muscle, the subject of observation. 

 I would add, however, that the results obtained in my earlier experi- 

 ments did, though open to these objections, seem to accord with those 

 I have obtained after sections at the base of the brain ; it may be that 

 the harmony between the two sets is superficial rather than real. 

 The experiments from which the results related here are quoted are 

 only those in which neither the orbit nor the cavernous sinus was 

 opened at all. 



It appears, therefore, that the activity of the internal straight 

 muscle can be directly inhibited by appropriate excitation of certain 

 parts of the frontal cortex, still better of the occipital cortex, of 

 the hemisphere of the side opposite to the muscle ; and the inhibi- 

 tion is very similar to that exerted over the activity of the external 



