278 



The Factors in Rhythmic Activity of the Nervous System * 

 By T. Graham Brown (Carnegie Fellow). 



(Communicated by Prof. C. S. Sherrington, F.R.S. Received April 11, — 

 Read May 16, 1912.) 



(From the Physiology Laboratory of the University of Liverpool.) 



I. Introduction. 



In a communication upon the intrinsic factors in progression presented to 

 the Society in July of last yearf the author drew the conclusion that the 

 rhythm of progression is of central origin. In then enquiring into the 

 nature of that central origin he suggested that the movements are deter- 

 mined by a balance between equal and opposite states of excitation — flexion 

 producing and extension producing.} 



An obvious line of research is thus presented by the possibility that reflex 

 stimuli which normally evoke opposite reactions (flexion and extension), 

 that is, opposite states (of excitation and inhibition) in one and the same 

 centre, when applied at the same time and with appropriate strengths of 

 stimulus may give a rhythmic response. 



When that communication was made such experiments had actually been 

 performed and had yielded positive results. The facts were not recorded 

 because it was intended to give them in greater detail at a later date. They 

 have been embodied in a thesis presented to the University of Edinburgh ; 

 but as some time must pass before they can be published in full it is desired 

 to give a brief account of them here. 



II. Methods. 



The muscles selected for examination were tibialis anticus and gastrocnemius 

 — a flexor and an extensor of the ankle. These were prepared in a manner 

 already described,} and their movements in response to stimulation of the 

 ipsilateral and contralateral long saphenous nerves examined. The muscles 

 wrote, by means of levers attached by threads to their tendons, upon the 

 blackened surface carried by a kymograph. 



* The expenses of this research have been defrayed by a grant from the Carnegie 

 Trust. 



t ' Roy. Soc. Proc.,' 1911, B, vol. 84, p. 308. 



% 'Quart. Journ. of Exp. Physiol.,' 1911, vol. 4, p. 331. 



