1893.] Correlation of Action of Antagonistic Muscles. 407 



improvement in diagnosis and more careful certification of the causes 

 of death. 



IV. " Further Experimental Note on the Correlation of Action 

 of Antagonistic Muscles." By C. S. Sherrington, M.A., 

 M.D. Communicated by Professor M. Foster, Sec. R.S. 

 Received April 15, 1893. 



(From the Physiological Laboratory of St. Thomas's Hospital, London.) 



Appropriate excitation of the afferent nerves from the flexor 

 muscles of the knee joint so alters, as I have shown,* the condition 

 of the extensor muscles of that joint that the reaction called the " knee 

 jerk " becomes no longer elicitable. I have endeavoured to examine 

 the quality of the alteration which thus restrains or abolishes the 

 " jerk." 



It must be remembered that there is some variance of opinion as 

 to the nature of the jerk itself. In the opinion of some authorities 

 the jerk is of reflex nature (Bowditch, Lombard, Senator, Warren) ; 

 in the opinion of others it is not truly reflex, but is a direct muscular 

 reaction, intimately dependent, however, on a reflex tonus in the 

 muscle (Tschiriew), or on a spinal influence reflexly exerted, but 

 not necessarily identical with "tonus" nor necessarily measurable 

 by tonicity (Waller). 



On the reflex theory of the "jerk," its disappearance or decrease 

 under excitation of the sensory nerve from its antagonistic muscles 

 tallies with phenomena of the mutual interference of spinal activities 

 such as are exemplified perhaps most clearly by those experiments of 

 Groltz, in which, after section of the spinal cord in the thoracic region, 

 the act of micturition could be cut short by strong stimulation of the 

 skin of the tail. On the view that the jerk is not itself reflex, but 

 depends on a reflex tonus, the abeyance of the phenomenon under 

 excitation of the afferent fibres of the hamstring nerve might be 

 owing to decrease thus induced in the tonus of the vasto-crureus 

 muscle, just as on the same view abolition of the jerk by cutting the 

 sensory roots of the crural nerve is due to the impairment thus pro- 

 duced in the tonicity. 



As a step toward determining between these two possibilities, I have 

 attempted to discover whether afferent impulses ascending- from the 

 hamstring muscles affect to any considerable extent the tonus of the 

 antagonistic quadriceps extensor. Complete abeyance of the "jerk" 

 under excitation of the hamstring nerve cannot, so far as I have seen, 

 be long maintained. After a longer or shorter interval the jerk 



* ' Koy. Soc. Proc.,' February 1, 1893. 



