712 tRANSACTIONS OF SECTION L 



is based upon developmental bistory and upon tbe suggestive fact tbat eacb nerve 

 cell forms an independent tropbic centre for its own distributed processes. It is 

 undoubted tbat, like tbe atomic theory in cbemistry, tbe neuron tbeory bas proved 

 of enormous service, enabling neurologists to disentangle tbe woven strands of 

 nerve-cell processes even in sucb an intricate woof as tbat of the central nervous 

 mass. There are, however, difficulties associated -with its full acceptance in 

 physiology, as indeed there are said to be in connection with the full acceptance 

 of the atomic theory in cbemistry ; but dismissing these for the moment, I pass on 

 to consider tbe presumable character of such a conception of nervous activities as 

 would be demanded on the supposition tbat tbe nervous system is, as regards all 

 essentials, an automatic physico-chemical mechanism. 



In the nerve fibres, which are undoubtedly tbe offshoots of nerve cells, tbe 

 only demonstrable changes during the actual passage of nervous impulses are of 

 an electrical type. These resemble tbe effects which would occur if there were 

 redistributions of sucb electrolytes as are known to exist witbin and around the 

 differentiated fibrillated core or axon of each nerve fibre. All the better-known 

 aspects of nerve-fibre activities are in accordance with such an electrolytic con- 

 ception. The exquisite sensibility of nerve to physical and chemical changes of a 

 sudden character would be associated with tbe fluctuating and variable character 

 of electrolytic distribution, this instability being characteristic of particular 

 electrolytes in colloidal solutions ; hence physical and chemical alterations 

 primarily affecting tbe nerve envelope will, by modifying the electrolytic distribu- 

 tion, produce physico-chemical change in tbe internal axon itself Sucb changes, 

 when once produced at any point in tbe differentiated fibrillar continuum of the 

 nerve fibre, must in accordance with the conception first propounded by Her- 

 mann be propagated or transmitted along this continuum. Tbe redistribution of 

 electrolytes at the seat of the external impression being itself a source of electro- 

 motive efl'ects, electrical currents demonstrably flow from this point into the 

 contiguous parts of the fibrillar continuum. Such flow of current must reproduce 

 in this neighbouring continuum that electrolytic redistribution which is tbe 

 fundamental aspect of nerve-fibre activity. Thus, by this comparatively simple 

 automatic mechanism, tbe physico-chemical electrolytic change is successiAely 

 assumed by tbe various portions which compose the length of tbe differentiated 

 axon, and the new or active phase is propagated along a nerve fibre as infallibly 

 as a flame speeds along a fuse when one end is ignited ; in this way tbe conception 

 explains how a so-called nervous impulse is brought into being. Further, tbe brief 

 duration of the activity of the nerve, its rapid development and slower decline, and 

 tbe circumstance that a second external change cannot arouse a second activity if 

 it occurs very shortly after an effective predecessor, all have their counterpart ou 

 the electrolytic side, and we have convincing evidence tbat the electrolytic 

 redistribution during activity cannot be again produced until tbe electrolytic con- 

 dition bas more or less returned to its original resting poise : tbe real peculiarity 

 of the living tissue is its persistent tendency to re-establish tbe electrolytic con- 

 centration of this resting poise. ^ Finally experiments show more and more con- 

 vincingly that the capacity of tbe nerve to respond to external changes, as well 

 as tbe magnitude and duration of tbe aroused activities, are particularly suscep- 

 tible to modiflcation by all those agents which are most potent in affecting electro- 

 lytic aggregates, such as temperature, electrolysis, and impregnation with various " 

 electrolytes. 



These electrical indications of nerve-fibre activities are fundamentally the 

 same whether the fibres occur in peripheral nerve trunks or in the bundles 

 which course through the central masses ; and thus, if tbe whole system con- 

 sisted of nothing but tbe united strands of differentiated nerve fibres, nervous 

 phenomena would be merely tbe expression of the development, along appro- 

 priately distributed tracts, of similar electrolytic changes primarily started 

 by some external physical or chemical alteration. But additional complications 

 are introduced by tbe existence of nerve-fibre endings and by the interposition 



' Gotcb and Burch, Journ. of Physiul., vol. xxiv. 1890, p. 410. 



