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.
The heart, the centre of organic life, and the brain, the centre of animal life, the two culminating organs of the living machine, are in an incessant relation of action and reaction which shows itself in two principal states,—syncope and emotion; the first due to the momentary cessation of the cerebral functions through intermission in the arrival of the arterial blood; the second due to the transmission to the heart of a circulatory modification. There is always an initial impression which slightly arrests this organ (according to[according to] Claude Bernard), whence a passing paleness, then a reaction which the heart, by reason of its extreme sensibility, is the first to feel; for, as the brain is the most delicate of the organs of the animal life, the heart is the most sensitive of the vegetative vital organs.
When it is said that the heart is broken by grief, this expression corresponds to actual phenomena. The heart has been arrested by a sudden impression, whence, sometimes, syncope and nervous attacks. The heart’s being “big,” answers to a prolongation of the diastole, which causes a feeling of fulness and oppression in the præcordial region. The “palpitation” of the heart is not merely a poetic formula, but a physiological reality; the beats being rapid and without intensity. The facility with which the heart is emptied, the regularity of the circulation being kept up by slight pressure, corresponds to the “light” heart. Two hearts beat “in unison,” under the influence of the same impressions. In the “cold heart” the beats are slow and quiet, as if under the influence of cold; in the “warm” heart, the contrary is the case. When we tell a person that we love him “with all our heart,” this expression signifies, physiologically speaking, that his presence, or the recollection of him, awakens in us a nervous impression, which, transmitted to the heart by the pneumogastric nerve, causes in our heart a reaction of such a kind as to produce in the brain a sentiment or an emotion. In man, the brain, in order to express its feelings, is obliged to take the heart into its service.[[82]]
Let us further recall the well-known observations of Mosso, who was able directly to study the circulation of the blood in the brain in three patients, in whom the cranium had been destroyed by various accidents. He ascertained that the mere fact of looking attentively at one of his patients, the entrance of a stranger, or any other occurrence of slight importance, immediately quickened the cerebral pulse. In one, a woman, the height of the pulsations suddenly increased, without apparent cause; she had just perceived in the room a death’s-head, which somewhat frightened her. The same thing took place with another patient when he heard the clock strike twelve; this was because he did not feel able to say his noon prayers. I do not dwell on his researches by means of the plethysmograph, which have special relation to intellectual work.
It will therefore be understood how popular opinion has come to look upon the heart as the seat, or the generator, of emotions. This is the instinctive expression of a quite correct view: the supreme importance to the affective life of the visceral action summed up in a fundamental organ.
II.
Since, for the moment, we are eliminating movements in order to confine our attention to the internal conditions of emotion, it is easy to see that these conditions reduce themselves to that which we designate by the name of internal, organic, vital sensations. This is not the place to enumerate the modifications of each in the case of each special emotion (for which the reader is referred to Part II.); the question, taken for the present in its generality, is put thus: Are the internal sensations reducible to a single and fundamental process? If the answer is in the affirmative, the internal conditions of emotion would find themselves simultaneously determined under their most general form. We can, at any rate, try.