In memory (the faculty of reproducing former sensations) and in imagination (the faculty of creating new ones) each hemisphere appears to create or to reproduce a sensation. If both are not perfectly correspondent, the perception of the mind which is to combine them, will be imperfect and irregular. Now, there must certainly be an inequality in the two sensations, if it exists in the two hemispheres which are the seats of these sensations.
Perception, memory, and imagination are the ordinary bases of the judgment: if the former are confused, how will the latter be distinct?
We have supposed an inequality of action in the two hemispheres, to prove that a defect of precision in the intellectual functions, must be the consequence; but what we have taken hitherto as supposition only, becomes reality in a multitude of instances. What is more common than to see produced from a compression on one of the hemispheres, by blood, by extravasated pus, a depressed bone or an exostosis on the internal surface of the cranium, numerous alterations in memory, perception, imagination, and judgment?
Even after every sign of actual compression has disappeared, if, still under the influence of that which it has just experienced, one side of the brain should remain enfeebled, are not these alterations prolonged in the same proportion? Are not various alienations of the mind the unhappy consequences? If both sides should be equally affected, the judgment would be weaker, but it would be more exact. It is in this way only that we can explain a fact often observed, that a blow upon one of the lateral regions of the head has re-established the intellectual functions which had been long disturbed in consequence of a prior blow received upon the opposite region.
I trust I have made it apparent that the intellectual functions must be disturbed, by an inequality of action in the
