On the brain and nervous system alcohol acts as a narcotic. If a dose is taken sufficiently large to produce intoxication, then, although the successive phases of inebriation cannot be sharply distinguished and each case has its own peculiarities, yet, broadly, three main stages can be made out.

In the first stage, there is a weakening of self-control, and a blunting of the power of self-criticism. In the second, the nervous functions controlling skilled movements and sense-perceptions are involved; there is a certain clumsiness of behaviour, an impairment of vision, hearing, etc., and also emotional instability; while as the narcosis proceeds, dulness and heaviness, dreamy somnolence, or actual sleep may supervene. In the third stage, " the intellectual processes of judgment and self-criticism and control are virtually suspended; the functions of sense-perception and skilled movement are grossly impaired; and the emotional tendencies themselves are invaded and weakened, so that only strong appeals to them suffice to evoke any response, and, in their absence, the drinker sinks inert and nerveless into a heavy sleep, which lasts until the alcohol absorbed by the nervous system has been oxidised or carried away in the blood and consumed by other tissues."1

1 Stockard; American Naturalist, 1913, 47; 1916, 50; Proc. Soc. Exp. Biol. Med., 1912, 9; 1914, 11.

2 " Alcohol, its Action on the Human Organism," p. 104.

These three main stages correspond with the invasion by the narcotic of the three principal levels of cerebral function, namely (1), the higher intellectual faculties, the latest acquired in the development both of the individual and of the race; (2), the sensory and skilled motor functions and their nerve-centres; and (3), the emotional capacities, a very ancient endowment, situated in the basal ganglia - the part which is alone represented in the brains of the lower vertebrates. Alcohol successively weakens and suspends these functions in the order given, from above downwards. The higher intellectual faculties are the first to suffer; then follows the narcotising of the sensory and skilled motor centres, and finally even the emotional faculties are weakened and therefore offer more resistance to the current. (Merely as an illustrative analogy, we may picture an electric current passing through a copper rod divided into a large number of segments; if at one end of the rod the segments are pressed firmly together the current passes easily; if, at the other, the segments barely touch one another the current passes the junctions only with difficulty.) If it is assumed that alcohol acts equally on all the synapses (nerve-cell junctions), equally increasing their resistances, it will first raise the resistance to the point of non-conductivity at those junctions where the normal resistance is already greatest - that is, in the later-developed levels, where the mental functions are highest; and it will progressively effect a similar paralysis of the other nerve-paths. Thus the higher intellectual centres would be the first paralysed, then the sensory and skilled motor centres, and finally the emotional centres; which is the order actually observed to occur.1

There appears to be no certain evidence that alcohol acts as a stimulant on the nervous system. The passing phase of initial exhilaration or excitement often observed in the early stages of intoxication may, not improbably, be attributed to the influence of festive environment acting upon the emotions, the control of which by the intellect and by the will has been diminished through the action of the alcohol taken. Apart from a possible exception as regards a small or moderate dose of alcohol acting on the respiratory nerve-centres, the conclusion arrived at from a study of the experiments recorded is that the direct effect of alcohol upon the nervous system is, in all stages and in all parts of the system, to depress or suspend its functions. In short, alcohol acts as a narcotic drug from first to last.

To explain the successive stages of the action of alcohol on the brain, as above described, the following hypothesis has been put forward. Alcohol acts primarily and most powerfully, not upon the nerve-cells themselves, or on the nerve-fibres, but upon the junctions (synapses) between nerve-cells. The nervous system may be regarded as made up of a large number of cells, each consisting of a central body and one or more fibres, and each cell having no anatomical continuity with others, but only a functional one. The points of contact of the cells are the weak points of the nervous pathways. They are the points which give way most readily under strain or shock and under the influence of fatigue, and of various paralysing drugs. Further, there is good reason to believe that in the lower levels of the brain the points of junction are relatively firm and open to the passage of the nervous current, whereas those of the higher and later-developed levels are less solidly organised,

1 "Alcohol, its Action on the Human Organism," pp. 35, 36.