appear,[81] ablated both the hemispheres of a dog, and kept him alive 51 days, able to walk and stand. The corpora striata and thalami in this dog were also practically gone. In view of such results we seem driven, with M. François-Franck,[82] to fall back on the _ganglia lower still_, or even on the _spinal cord_ as the 'vicarious' organ of which we are in quest. If the abeyance of function between the operation and the restoration was due _exclusively_ to inhibition, then we must suppose these lowest centres to be in reality extremely accomplished organs. They must always have done what we now find them doing after function is restored, even when the hemispheres were intact. Of course this is conceivably the case; yet it does not seem very plausible. And the _a priori_ considerations which a moment since I said I should urge, make it less plausible still. For, in the first place, the brain is essentially a place of currents, which run in organized paths. Loss of function can only mean one of two things, either that a current can no longer run in, or that if it runs in, it can no longer run out, by its old path. Either of these inabilities may come from a local ablation; and 'restitution' can then only mean that, in spite of a temporary block, an inrunning current has at last become enabled to flow out by its old path again--e.g., the sound of 'give your paw' discharges after some weeks into the same canine muscles 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,[83] the only question before us is: Is the formation of _these particular 'vicarious' paths_ too much to expect of its plastic powers? It would certainly be too much to expect that a hemisphere should receive currents from optic fibres whose _arriving-place_ within 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 irreparable _within 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 incoming 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 affected 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 _somewhere_; and if it only once succeeds by accident in striking into its old place