1893.] Correlation of Action of Antagonistic Muscles. 415 



corresponding to the nerve section, although the opening of the eye 

 the other side is each time quick and wide. That is to say, there is 

 in this instance no evidence of concomitant activity of the antagonistic 

 muscle, either in the sense of contraction or of relaxation. But on 

 shifting the electrodes to the suitable point of the cortex the eyes of 

 both sides reply to the excitation by a sharp closure just as usual. 



The well-known dilatation of the pupil elicitable from this region 

 of the cortex might, in view of the abo re-described examples of in- 

 hibition from the cortex, perhaps, be supposed to be related rather to 

 an inhibition of the constrictor action of the 3rd nerve than to 

 cortical augmentation of the influence kept up via the cervical sym- 

 pathetic. The dilatation of the pupil under excitation of the frontal 

 cortex certainly is much later in onset than are the movements of the 

 extrinsic ocular muscles, but that difference might be based on the 

 difference in time of response of the two kinds of muscular fibres in- 

 volved. This supposition is, however, negatived by the fact that 

 division of the cervical sympathetic cut out dilatation that was being 

 regularly elicited from the cortex, the 3rd nerve being undivided, 

 in two experiments I made to test the point. In these instances, 

 therefore, although an extreme dilatation was obtained with, for the 

 cortex, quite weak currents, the cortex reacted by discharge directed 

 through the sympathetic system. 



Addition. April 20, 1893. 



I would add to the above the following remarkable passage, which 

 I find in 1 The Anatomy and Physiology of the Human Body,' by 

 Charles and John Bell (London, 1826, vol. 3). In describing the 

 action of the muscles of the eye, the author, after adverting to some 

 experiments made by himself on the functions of the 4th cranial 

 nerve, says : — 



" We have seen that the effect of dividing the superior oblique was 

 to cause the eye to roll more forcibly upwards; and if we suppose 

 that the influence of the 4th nerve is, on certain occasions, to cause a 

 relaxation of the muscle to which it goes, the eyeball must be then 

 rolled upwards. 



" The nerves have been considered so generally as instruments for 

 stimulating the muscles, without thought of their acting in the oppo- 

 site capacity, that some additional illustration may be necessary here. 

 Through the nerves is established the connection between the 

 muscles, not only that connection by which muscles combine to one 

 effort, but also that relation between the classes of muscles by which 

 the one relaxes and the other contracts. I appended a weight to a 

 tendon of an extensor muscle, which gently stretched it and drew 

 out the muscle ; and I found that the contraction of the opponent 



