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Page:Popular Science Monthly Volume 4.djvu/575

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nature of the nerve-connections of the heart with the brain were as yet unknown, and a Russian physiologist, E. Cyon, has, for some years past, labored successfully to fill up this gap. The heart is provided with a number of little self-acting nerve-ganglia, without relations to the brain, from which spring, under the influence of the blood, a certain number of motor impulsions. These ganglia govern the usual normal action of the cardiac apparatus; but the rhythm and the force of the beatings are every instant modified by excitations having their origin in the brain. The latter organ sends out to the ganglia of the heart two sets of nerves—the pneumogastric, or retardator, and the accelerator nerves. Excitation of the former diminishes the frequency and augments the force of the heart's movements. The accelerator nerves produce the opposite result, increasing the number and lessening the force of the heart's contractions. These two sets of nerves accommodate the activity of the heart to that of the rest of the organism, and hold it in equilibrium with the continual oscillations of the various functions of body and soul. Besides these filaments, extending from the brain to the heart, there are others from the heart to the brain, which M. Cyon calls depressors. The office of these nerves is to notify the brain, and consequently the soul, of the changes occurring in the rhythm and energy of the cardiac contractions. Thus, in virtue of the pneumogastric and the accelerator nerves, the heart is an organ whereon is reflected, immediately and with precision, every passional state, with its nicest shades of distinction. And, on the other hand, in virtue of the depressor-nerves, our consciousness notes the infinitely-diverse oscillations of the heart's beatings attendant on passional states. The mechanism of the heart's motions under passion depends on these two inverse nerve-currents.

Every agreeable or joyous emotion of the soul excites the accelerator nerves of the heart, and causes that organ to beat with great rapidity, lessening at the same time the force of its contractions. The phrases, the heart leaps with joy, or flutters with joy, admirably characterize this action of the accelerator nerves. The facility with which the heart drives the blood into the arteries, under such circumstances, produces that feeling of comfort and pleasure which is expressed by the words, a light heart. On the other hand, all sad or painful feelings act chiefly on the retardator fibres of the pneumogastric nerves. Emotions of this description diminish the rapidity of the heart's beatings, and so increase the amount of blood discharged from that organ at each diastole; hence the contractions by which it drives the blood into the vessels are laborious and protracted. These contractions, attended as they are with pain, give rise to an ensemble of sensations, expressed in common language by such phrases as oppression of the heart, the heart is agonized, etc. That other phrase, the heart is ready to burst, expresses, with great exactitude, the sensation of stricture one feels when suffering from pent-up anguish. The news of some