A cytophotometric measurement of protein concentration and content in the neuronal cytoplasm and in the structures surrounding the neurones was made with the view of studying the plastic properties of units in individual layers of the visual cortex. The data obtained attest that the absence of specific impulse activity from the moment of birth up to 2.5 months brings about a distinct rise of concentration and a drop in protein content along with a decrease of the cytoplasm surface of neurones in layer IV and large pyramides of layer V as well as a decrease of protein concentration in the structures surrounding the neurones in the lower part of layer III, in layer IV and in the area of large pyramids in the layer V. It is suggested that such changes are related to the fact that neurones belong to groups differing in the degree of reactivity of biochemical changes, depending on their functional significance.