310 THE BODY AT WORK 



stimulated with a rapidly interrupted current. The muscles 

 which it governs contract with their natural rhythm. The 

 cortex is sliced away, and the stimulus applied to the white 

 matter beneath. A similar result is obtained. Evidence 

 such as this points to an independence of action on the part 

 of the neurones which one can express only in terms of re- 

 sistance and explosion. But there is another line of thought 

 which leads to the development of a picture of the working ner- 

 vous system which seems at first sight incompatible with the 

 one that we have sketched. The phenomenon of the knee-jerk 

 (p. 274) reveals a nervous system so intimately linked together, 

 so homogeneous, so mobile, that no event, however trivial, 

 occurs in any part without sending a vibration throughout the 

 rest. Instead of a multitude of batteries enveloped in a 

 labyrinth of wires interrupted by myriads of switches which are 

 crackling on and off, the image of a sheet of water better 

 figures our conception a material so frictionless that it is 

 a-ripple from side to side and end to end, from the most distant 

 rivulet which feeds it to the farthest trickle in which it drains 

 away. It is a fluid in a state of infinite commotion, the 

 movements of its particles varying in amplitude from tremulous 

 quiverings which scarcely frost the silver of its surface to waves 

 which, breaking on the muscular system, throw it up in heaps. 

 The vinegar experiment seems to demand a scheme of batteries 

 and wires. The knee-jerk points to a continuous conducting 

 medium. Other phenomena suggest the superposition of the 

 two pictures ; the conception of a nervous system consisting 

 of a uniform medium conducting, not indifferently in all 

 directions, but with such freedom that from our point of view 

 the paths are infinite in number ; and within this conducting 

 medium nerve-cell bodies and their processes which collect 

 and distribute groups of vibrations sufficiently strong in com- 

 bination to produce visible effects. In order that one of these 

 neurones may be stimulated to discharging-point, the medium 

 by which it is surrounded must be thrown into such a state of 

 agitation as suffices to infect it. The considerations which 

 point to the formulation of this double or superposed scheme are 

 such as follow : The passage of tone-impulses does not appear 

 compatible with the ideas we have formed on other evidence 

 of synaptic resistance and neuronic discharge. They are too 



