132 



On the Question of Fractional Activity (" All or None " 

 Phenomenon) in Mammalian Reflex Phenomena. 

 By T. Graham Brow (Carnegie Fellow).* 



(Communicated by Prof. C. S. Sherrington, F.R.S. Received June 17, — 

 Read June 26, 1913.) 



(From the Physiological Laboratory, University of Liverpool.) 



CONTENTS. 



PAGE 



I. Introduction 132 



II. The Experimental Evidence 132 



III. Objections to " all or nothingness " 134 



IV. Methods here employed 136 



V. Eesults 137 



VI. Conclusions 139 



VII. Summary 141 



I. Introduction. 



At the present moment the question whether or not there is a state of " all 

 or nothing " activity in reflex arcs seems to be raised, and it is one of 

 importance to the future of investigation of the functions of the nervous 

 system. 



Of the two views which may be held regarding the manner of the activity 

 of reflex arcs one is that in which it is supposed that the efferent neurone 

 may react with different degrees of intensity in different reflex activities, and 

 that the afferent neurones may play with different degrees of intensity upon 

 efferent neurones or upon interposed neurones. 



The other view, which seems now to be dawning, is one in which it is 

 supposed that the efferent neurone has no grading in the intensity of its 

 activity — it either reacts maximally or not at all ; and if this be demon- 

 strated it may perhaps be inferred that the afferent neurones act in a similar 

 manner — that is, that their activity is either " all or none." 



It is obvious that, if either of these views is shown to be the correct one, 

 the course of research will in the future be modified. 



II. The Experimental Evidence. 



There is, at present, little direct experimental evidence bearing upon the 

 question of " all or nothing." activity in reflex arcs. 



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

 Trust. 



