The Neurone Theory in the Light of Recent Discoveries

Abstract

THE nervous system differs from all other systems of organs in that its cellular elements show the highest degree of differentiation. Thus, in the digestive system, the destruction of a few liver cells means only a minute diminution in the amount of bile secreted, a loss that can be entirely replaced through the slightly increased activity of the remaining cells; and in the muscular system the removal of a few muscle fibres from a given muscle may be made good physiologically by a minimal increment of work from the remaining fibres; but the loss of a few or even of a single sensory cell in the retina will produce a blind spot in that organ which no amount of activity from the adjoining cells, aside from possible regeneration, can ever replace. Each sensory cell in the more efficient parts of the retina has a function dependent upon its position and, therefore, different from that of any neighboring cell; and, while this may not be absolutely true of all parts of the nervous sys-