We therefore perceive how even more important than for other organs it is, that the circulation of the brain, the tissue of which is the most delicate and sensitive, should remain unaffected by over-stimulation of the heart's action, which, in reality and effect, is the controlling power of the system, and may be likened to an engine, by means of which is kept in operation the force requisite to move the machinery of all other portions of the system, and maintain them in harmonious activity. But, let us study this physiological effect of alcohol a little further, that we may more fully understand how much is signified by it. Every heart-beat causes a certain amount of blood to pass through the larger arteries to the brain, and thence through its minute vessels or capillaries. It is by means of the capillary circulation that the brain, its cells, connective tissues, and all membranes, are supplied with the requisite material for life and activity. So important is the _regularity_ of this supply to the brain in the discharge of its functions, that a special arrangement of blood-vessels is provided, or rather the number of arteries is larger and their distribution more complicated and various than for any other organ. If now this supply of blood is increased by one fourth or one sixth, or in any other degree, through the action of the heart, there must result a relative increase of it to the brain-cells and tissues, together with a corresponding increase of function. The anatomy of the brain teaches us that every fibre, brain-cell, and even nucleus, is enclosed with an exceedingly thin covering, through which its contents may be nourished, and also through which, when its constituents are no longer of any use, they may be eliminated and removed from the body. These coverings, or membranes, as they are called, in turn, derive their materials for growth and function from the minute capillary blood-vessels which, in almost infinite number, supply them, while all portions of brain tissue are together dependent upon the _regularity_ of the heart's supply of blood to enable them to discharge their functions in a normal manner. Now, physiological experiments have shown that the effect of alcohol upon that portion of the nervous system--the vaso-motor--which presides over and supplies power of action to these capillaries, and also regulates the action of the heart, is that of a narcotic. Its effect is to partially paralyze this nerve, and leave the heart to act more freely and rapidly under the influence of the motor nerve; in consequence of this partial paralysis of the coats of the capillary vessels, when the blood passes through them so much more rapidly than when in their normal state, they fail to absorb from the blood the material requisite to nourish them, and also fail to remove material which has already been used.