Cellular Interactions and Interdependence during Development of the Nervous System

Abstract

It will have become clear from the preceding chapters of this book that the manifold and diverse components of the developing nervous system provide each other with a mutual environment and produce reciprocal effects as a result of their competitive and their cooperative interactions. Nothing in the organism is completely autonomous: every part, however free and fundamental it may seem to those with a limited point of view, is dependent on its mutual relations with other parts of the organism. As Claude Bernard, in his Introduction to the Study of Experimental Medicine, (1865) puts it, “The properties of living bodies are revealed only through reciprocal organic relations. A salivary gland, for instance, exists only because it is in relation with the digestive system, and because its histological units are in certain relations one with another and with the blood. Destroy these relations by isolating the units of the organism, one from another in thought, and the salivary gland ceases to be.” But later in the same work he says, “It is doubtless correct to say that the constituent parts of an organism are physiologically inseparable from one another, and that they all contribute to a common vital result; but we may not conclude from this that the living machine must not be analyzed as we analyze a crude machine whose parts also have their role to play in a whole.