272 PROTOPLASMIC ACTION AND NERVOUS ACTION 



may be initiated, since the same effect will be repeated 

 at each newly formed boundary between the active and 

 the inactive areas. 



According to this conception the primary action of a 

 local stimulating agent is to change rapidly the electrical 

 condition of the cell-surface at its point of application. 

 The parallel between the irritable protoplasmic system 

 and the passive iron model is obvious, since in the latter 

 case also a local alteration of the surface-film involving 

 a local change of potential is the initiating condition for 

 the propagated wave of chemical and electromotor 

 disturbance. 



The present view, therefore, regards stimulation as 

 conditioned by surface processes of the foregoing def- 

 inite kind. If this is true, the structural arrangements 

 providing for the transfer of excitation from one irritable 

 element to another should exhibit features of a character 

 to correspond. In fact, many peculiarities of the 

 structure of the central nervous system — especially of 

 the synaptic junctions — and of the structure and arrange- 

 ment of nerve-endings, such as the myoneural junctions, 

 are in harmony with this conception. Nerve end-plates 

 spread out over the surface of the muscle cell, effecting 

 intimate contact but not penetrating; the junctions 

 between neurones are eft'ected by brushlike interlacing 

 terminals, or by end-feet and similar structures which 

 are applied to the cell surface with a closeness that 

 apparently admits of variation. That transmission by 

 contact, through the influence which the cell-process 

 exerts upon adjoining processes or upon the cell body, 

 is the chief mode of transmission in the nervous system 

 is one of the corollaries of the neurone theory of the 



