184 



Dr. H. Head. 



is required in the propagation of the electric response, and that the physico- 

 chemical change producing the response is the only factor involved in the 

 propagated nervous impulse. 



My thanks are due to Dr. E. D. Adrian and to Mr. E. H. Fowler, both of 

 Trinity College, Cambridge, to the former for experimental results and critical 

 suggestions, to the latter for help in the mathematical treatment of the 

 problem. 



A Method of Analysing Galvanometer Records. 

 By W. Harteee, M.A., and A. V. Hill, Sc.D., F.E.S. 



[This paper is printed in Proceedings, Series A, vol. 99, p. 172 (No. A 697).] 



Croonian Lecture : — Release of Function in the Nervous System. 

 By Henry Head, M.D., F.E.S. 



(Received April 22, — Lecture delivered May 5, 1921.) 



It is a common experience that the manifestations of nervous disease may 

 comprise both loss of function and some positive outburst of excessive 

 activity. Thus, in many cases of hemiplegia, the paralysed limbs tend to be 

 more or less rigid and the reflexes are greatly increased. This spasticity, 

 although due to a destructive lesion, was attributed to "irritation"; the 

 morbid agent, or the conditions it produced in the nervous system, were 

 supposed to have an " irritative " effect upon the tissues, and this was 

 expressed in the positive signs and symptoms. 



But more than fifty years ago, Hughlings Jackson [11]* laid down the rule 

 that destructive lesions never cause positive effects, but induce a negative 

 condition, which permits positive symptoms to appear. This he applied to 

 all morbid expressions of nervous activity ; but his most striking instance 

 was the motor condition in organic hemiplegia. He showed that it depended 

 on two factors. First, there was loss of voluntary power, especially in the 

 fingers, the parts most directly under cortical control ; this was the negative 

 * Numbers in square brackets refer to List of References at end. 



