The reason for it has become very clear as the result of our generation's investigations into the constitution of the nervous system. The central nervous system, instead of being a _continuum_, or series of nerve elements which are directly connected with each other, consists of a very large number of separate individual cells which only make contacts with each other, the nerve impulses flowing over across the contact. The demonstration of these we owe originally to Ramon y Cajal, the distinguished Spanish brain anatomist, to whom was awarded some years ago the Nobel Prize as well as the Prize of the City of Paris for his researches. In connection with his surprising discoveries as to the neurons which make up the brain, he suggested the Law of Avalanche, which would serve to explain the supersensitiveness of parts to which concentrated attention is paid. {124} According to this law, pain felt in any small area of the body may be multiplied very greatly if the sensation from it is distributed over a considerable part of the brain, as happens when attention is centered upon it. A pain message that comes from a localized area of the body disturbs under normal conditions at most a few thousand cells in the brain, because the area is directly represented only by these cells. They are connected however by dendrites and cell branches of various kinds with a great many other cells in different parts of the brain. A pain message that comes up will ordinarily produce only disturbance of the directly connected cells, but it may be transmitted and diffused over a great many of the cells of the cortex of the brain if the attention is focused strongly on it. The area at first affected, but a few thousand cells, may spread to many millions or perhaps even some hundreds of millions of them, if the centering of attention causes them to be "connected up", as the electricians say, with the originally affected small group of cells. It is just what happens in high mountains when a few stones loosened somewhere near the top by the wind or by melting processes begin their course down the mountain side. {125} On the way they disturb ever more and more of the loose pieces of ice and the shifting snows as well as the rocks near them, until, gathering force, what was at the beginning only a minor movement of small particles becomes a dreaded avalanche, capable not only of sweeping away men in its path but even of obliterating houses and sometimes of changing the whole face of a mountain area. Hence the expression suggested by Ramon y Cajal of the Law of Avalanche for this wide diffusion of sensation, which spreads from a few thousand to millions or billions of cells, and from a rather bearable pain becomes intolerable torture, as a consequence of the brain's complete occupation with it.