On the Nature of Inhibition: a Review.∗

While, during the last thirty years, great advances have been made in our knowledge of inhibition, its properties and its interactions with excitation, yet little progress has been made in elucidating the precise nature of inhibition itself. Pavlov (67), for instance, has discovered many of the principles of inhibition, its interaction with excitation, its irradiation, its extinction and so on. But all the time he is dealing with inhibition simply as a phenomenon which shows itself in the end-reaction. With regard to what is actually happening in the cortex, he admits that it is unknown. Yet the phenomenon of inhibition is one of prime importance in the organization of the central nervous system. Perhaps, at times, while watching, say, a dog chasing a ball, one is apt to forget the many reactions which are not happening in one's interest in what is happening. Yet an overdose of strychnine to the dog will soon remind one that every movement of each limb, every twitch of a muscle is surrounded, as it were, by a wall of inhibition, checking, controlling and timing so as to produce the final smooth and graceful co-ordination.