410 



Dr. C. S. Sherrington. Note on the 



[May 4, 



muscles became rigid earlier in the leg that had been flexed than in 

 the other. This is not what might have been expected in view of 

 Wundt's* observation that tension in a nrascle hastens rigor in it. 

 It must be remembered that Wundt's statement is not based on 

 muscle in situ, intact and connected with the spinal cord. The 

 observed fact harmonises with the existence of an augmentation of 

 tonus of extensors in result of excitation of the afferent nerves from 

 their opponent group. 



The experiments so far therefore seem to indicate that the direc- 

 tion of the change induced in the extensor muscles by afferent im- 

 pulses ascending from the flexors is in the direction of increased 

 tonicity, and to strengthen the supposition that the interference with 

 the "jerk " is located in the spinal mechanism of the " jerk." 



The marked influence exerted reflexly by the flexors of the knee 

 upon the extensors of that joint suggested search for instances of 

 analogous correlation elsewhere. The delicately correlated muscles 

 of the eyeball offer an experimental advantage in that even slight 

 alterations of their length can be readily observed by inspection. 

 1 therefore exposed the inferior oblique muscle (Cat and Monkey), 

 completely detached it from the globus, and then observed the effect 

 of lightly drawing upon it, so as to stretch it between the end held 

 and the end attached to the bony floor of the orbit. Reflex actions 

 were in this way easily obtained, but were inconstant in character ; 

 the eyeballs were generally moved, perhaps most frequently conju- 

 gately, toward the side corresponding to the stretched muscle. 

 I watched especially to see whether the globes were turned upward 

 or downward, but those movements were far less frequent than move- 

 ments apparently purely lateral. Sometimes the reflex obtained did 

 not affect the eyes at all ; the movement was often a pricking of the 

 ear, either with movement of the eyes or apart from eye movement. 

 Twice the muscle was detached altogether with careful avoidance of 

 injury to its nerve and blood vessel ; held between two ivory-tipped 

 forceps, it was then gently stretched. The results were the same as 

 when its one end retained the natural attachment. In all cases, 

 section of the nerve which enters its posterior border to supply it 

 immediately abolished all reply. This nerve is relatively long and 

 easily isolable. Electrical excitation of it can be performed with 

 facility ; a weak tetanising current applied to its central end pro- 

 duced the same variable movements as did the stretching of the 

 muscle itself, but apparently less readily. 



The inferior oblique muscle was employed for these observations 

 because it can be freely isolated with little injury and displacement 

 of other structures, and because of the length of the nerve branch 

 supplying it. I should have preferred, otherwise, to use the externus 

 * ' Die Lehre der Muskelbewegung,' pp. 68 — 72. Brunswick, 1858. 



