FUNCTIONS OF THE BKAlN. 71 



weeks into the same canine mnscles into which it used to 

 discharge before the operation. As far as the cortex itself 

 goes, since one of the purposes for which it actually exists 

 is the production of new paths,* the only question before 

 us is : Is the formation of these particular ' vicarious ' paths 

 too much to expect of its plastic powers ? It would cer- 

 tainly be too much to expect that a hemisphere should 

 receive currents from optic fibres whose arriving-place with- 

 in it is destroyed, or that it should discharge into fibres of 

 the pyramidal strand if their place of exit is broken down. 

 Such lesions as these must be irrejjarable luithin that 

 hemisphere. Yet even then, through the other hemisphere, 

 the corpus callosum, and the bilateral connections in the 

 spinal cord, one can imagine some road by which the old 

 muscles might eventually be innervated by the same in- 

 coming currents which innervated them before the block. 

 And for all minor interruptions, not involving the arriving- 

 place of the 'cortico-petal' or the place of exit of the 'cortico- 

 fugal' fibres, roundabout paths of some sort through the 

 afi'ected hemisphere itself must exist, for every point of it 

 is, remotely at least, in potential communication with every 

 other point. The normal paths are only paths of least 

 resistance. If they get blocked or cut, paths formerly more 

 resistant become the least resistant paths under the changed 

 conditions. It must never be forgotten that a current that 

 runs in has got to run out someichere ; and if it only once 

 succeeds by accident in striking into its old place of exit 

 again, the thrill of satisfaction which the consciousuess 

 connected with the whole residual brain then receives will 

 reinforce and fix the paths of that moment and make them 

 more likely to be struck into again. The resultant feeling 

 that the old habitual act is at last successfully back again^ 

 becomes itself a new stimulus which stamps all the exist- 

 ing currents in. It is matter of experience that such feel- 

 ings of successful achievement do tend to fix in our memory 

 whatever processes have led to them ; and we shall have 



* The Chapters on Habit, Association, Memory, and Perception wiU 

 change our present preliminary conjecture that that is oue of its essential 

 uses, into an unshakable conviction. 



