Croonian Lectures ON THE PULSE
The nutrition of the brain, as of all parts of the body, is dependent upon the supply of an adequate amount of healthy blood, but the functional activity and efficiency of the brain is even more dependent upon the blood-supply than its nutrition, and is influenced by it to an extraordinary degree, so that blood which would maintain the structural integrity of the brain might be altogether unfit to minister to its functions. The presence of alcohol in the blood, for example, does not interfere
... oes not interfere with the nutrition of the nerve centree, but it deranges their action, and poisons generated in the system or retained excretory matters may have a similar effect. The liberation of nerve force has been represented as an explosive action, and this implies the presence in the nerve cells of a substance ready, on the application of the proper stimulus, to combine instantly with the oxygen brought by the blood. The formation of such material, its maintenance at a given state of chemical tension, so to speak, which differs in the different centres, in the cortex, in the central ganglia, and in the medulla and cord, is not paralleled by any other nutritive operation. There is, moreover, the further requirement of a due supply of oxygen. An illustration of the relation between cerebral functions and the circulation is seen in the ansemia of the cortex of the hemispheres during sleep. This bloodlessness is essential to sleep, and, if it can be induced, sleep follows.