It is well known that the vaso-motor nerves of the head, the upper limbs, the lower limbs, the viscera, are furnished in part by the nerve-reticulations of the sympathetic system, in part by the rachidian nerves issuing from different parts of the spinal cord. Now, an experiment of Claude Bernard’s, made as far back as 1852, shows that the section of the great sympathetic in the neck produces on the same side an expansion of the vessels, and an increase in the temperature, nutrition, muscular tonicity, and sensibility. On the contrary, galvanism applied to the same nerve produces constriction of the vessels and the contrary phenomena to the preceding. Féré points out that the manifestations of the first case are, in general, those of the sthenic emotions, as those of the second are of the asthenic emotions.[81] Footnote 81: _Op. cit._, pp. 490, 491. Whatever we may think of this comparison, the incontestable and so often recorded characteristic of emotion—diffusion—shows us that it is everywhere; that, if we could see with our eyes the cerebral mechanism supporting it, we should be spectators of the co-ordinated work of the multiple centres; that, consequently, the hypothesis of a localisation, of a seat in the limited sense, is in no way justified. 2. It is needless to remind the reader that the majority of idioms make the heart the incarnation of affective life, and that the antithesis of reason and passion is, in current speech, that of the brain and the heart. This opinion is not entirely a prejudice, as contemporary physiologists have shown. Why is the heart, an unconscious muscle, promoted to the position of an essential and central organ of the emotions and the passions? It is so in accordance with the well-known physiological law which makes us transfer our psychic states to the peripheral organ which communicates them to our consciousness. It feels the rebound of all the impulses which strike us; it reflects the most fugitive impressions; in the order of the sentiments, no manifestation takes place outside it, nothing escapes it; it vibrates incessantly, though in different manners. Claude Bernard, and after him, Cyon, have undertaken to justify the popular expressions regarding the heart, to show that they are not mere metaphors, but the result of accurate observation, and that they can be translated into physiological language. I here summarise their principal remarks.