414 Dr. C. S.. Sherrington. Note on the [May 4, 



experiment has not succeeded unless this stimulation be somewhat 

 strong) will not unfrequently cause the right eye to move inwards 

 and sometimes fully up to the primary position. The active con- 

 traction of the external rectus appears to be cut short and even con- 

 verted into a condition of relaxation more complete than when no 

 cortical excitation at all is being employed. 



I have watched with interest in Macacus the voluntary movements 

 of the eyes after section of the 3rd and 4th nerves. In the early 

 hoars after the section, if for instance these nerves have been cut 

 on the left side only, the gaze is readily directed to the left but not 

 so readily to the right. There arises, of course, considerable external 

 squint of the left eye. Neither when the right is directed toward 

 the right nor when it is converged upon a light or other object just 

 in front of the face is there more than a mere trace of movement 

 of the left eye. Twenty- four or forty- eight hours later, when the 

 right eye is turned to right the left eye does perform the conjugate 

 movement, but imperfectly, and more imperfectly and also more 

 variably than under experimental excitation of the frontal cortex. 



Another instance in which antagonistic correlation may be examined 

 is that of the muscles which close and open the palpebral aperture. 

 These are at least potentially antagonistic. I find that in the 

 Monkey excitation of the 3rd nerve in the cranium slightly depresses 

 the lower eyelid at the same time that it freely raises the upper. 

 This slight depression, often very slight indeed, is abolished by 

 section of the branch of the 3rd to the inferior rectus muscle. The 

 3rd nerve (leaving out of consideration the cervical sympathetic, the 

 action of which in opening the eye, as regards speed, direction of 

 movement, and other characters, is different from the opening obtain- 

 able from the cortex) may be termed the nerve which opens the 

 palpebral aperture. The 7th is the only nerve which closes it by 

 active muscular contraction. 



This latter statement applies to the Monkey, not to the Cat, because in the Cat, 

 after section of the 7th nerve at the stylomastoid foramen, I find that, although the 

 upper and lower lids remain permanently rather widely apart, the third eyelid 

 (membrana nictitans) shuts at short intervals with an extremely rapid sweep com- 

 pletely over the exposed part of the globus ; and when after section of the 7th 

 the animal sleeps the nictitating membrane is partially extended over the front of 

 the ball. The third eyelid is therefore not innervated like the upper and lower 

 from the 7th. Langley and Anderson* record that it is not innervated from the 4th, 

 probably not from the 3rd, but that excitation of the 6th causes " great protrusion 

 of it." 



If, after section of the 3rd, the appropriate part of the frontal 

 cortex be excited either on the same side as the nerve cut or on the 

 opposite side I find no movement at all result in the lids on the side 



* ' Journ. of Physiol.,' vol. 13, p. 461. 



