To sum up, we may say that, in a given race, at a given moment of its development, there is a certain average of alimentary tastes, whose satisfaction is pleasurable; but on the appearance of deep-seated disturbances in the organism everything is changed, tendencies, desires, and aversions; the pleasurable and painful states, _which are merely effects_, vary with and in the same manner as their cause. The physiological acts, which have for their aim the maintenance of nutrition, scarcely enter into the consciousness, except under the guise of hunger and thirst, whose psychology cannot be studied here, because it forms part of another department—that of the sensations. All the phenomena previously enumerated are reducible to anomalies or deviations of hunger. The pathology of thirst is simpler, for it may be summed up as dipsomania, a condition whose modalities and clinical varieties have no interest as regards the psychology of instinct; but so far as this need is concerned, the transformation of the normal and natural tendency into a morbid one does not differ in its mechanism and results from what we have already stated in the case of hunger. There exist, in general and special treatises, many descriptions of dipsomania to which we may refer the reader. Leaving aside all hallucinations, motor disturbances, intellectual and moral decadence, we shall only consider the genesis, the development, and the consolidation of this morbid tendency. “It is not every one who can be a dipsomaniac.” To drink too much, whether voluntarily or by accident, is a thing which may happen to any one; but such an occurrence does not necessarily bear the fatal and inexorable character of an insatiable instinct. The period of incubation—_i.e._, of gradual action tending towards complete metamorphosis—presents clearly-marked psychological characteristics, showing a disturbed state of cœnæsthesia and belonging to the region of the emotions: _malaise_, sadness, lack of energy and courage, apathy, moral insensibility, vague presentiments of danger. After this the eruption takes place in the form of an intense, devouring thirst. Many try to react on this and cheat themselves by the aid of water or mucilaginous substances, which shows, as several writers on the subject have remarked, that alcoholism properly so called is only a paroxysm: under the pressure of a progressively intensified craving the decisive step is taken. We shall find a great variety in the numerous observations published on this subject, a struggle at the beginning only, a struggle preceding every attack, indignation of the patient against himself, under the influence of which he calls himself names, and forces himself to swallow strange and repugnant beverages; all these phenomena are found in various cases. To sum up, the history of this psychological metamorphosis is briefly this: incubation, formation of a fixed idea, obsession, final fall.