At first sight, and without entering into any analysis, every emotion, even of slight intensity, appears to us as affecting the entire individual, and expressing, in its complete form, what Bain has called the law of diffusion. Its external symptoms are movements of the face, the trunk, and the limbs; its internal, numerous organic modifications caused and dominated by the circulation—the organic function _par excellence_. The experiments of Lombard, Broca, Bert, Gley, Mosso, Tanzi, etc., have shown that any and every form of mental activity is connected with an increase in the circulation; but the latter is always above the average when an emotion is manifested. Emotional activity of a given kind, says Lombard, produces an increase of temperature in all parts of the body; it is, in general, more rapid and stronger than that which comes from intellectual activity. Mosso, who, by some well-known experiments, has been enabled to study even the slightest modifications of the circulation, concludes that “the action of the emotions on the cerebral circulation is much more evident than that of intellectual work, whatever its energy.” Emotion not only presents these vague and different characteristics, but every separate emotion is a complexus. Let us take the simplest and commonest—fear, anger, tenderness, sexual love; each one of them is a complete state in itself, a psycho-physiological fascicule constituted by a grouping of simple elements, differing with each emotion, but always comprising a particular state of consciousness, particular modifications of the functions of organic life, movements or tendencies to movement, arrest or tendencies to the arrest of particular movements. Every primary emotion is an innate complexus expressing directly the constitution of the individual; the emotions are _organised_ manifestations of the life of the feelings; they are the reactions of the individual on everything which touches the course of his life, or his amelioration, his being, or his better being. In a certain manner, the primary emotions are analogous to the perceptions, which require a psycho-physiological organism adapted to a special function in relation to the external world; with this difference, that sight, hearing, smell, etc., have their own special and inalienable organs, while fear, anger, etc., have a diffused organism, the elements of which, combined in another manner, become the organism of another emotion.