deserve notice here: but the constant motion of the blood is principally to be considered, being the cause as well as the effect of the constant motion of the heart.
Seventhly, Since lying down prevents or alleviates the fainting which sometimes happens during bleeding, one may suppose that this fainting, and the consequent abatement or cessation of the motion of the heart arise, because a quantity of blood, sufficient to keep up the vibrations in the brain, could not ascend thither in an erect posture.
Eighthly, Sudden and violent pains, such as those from wounds, increase the motions of the heart. This may be accounted for from the violent vibrations which ascend to the brain, and are thence propagated to the heart. But may not vibrations ascend also directly from the wounded part, along the course of the arteries and veins, to the heart?
Ninthly, All the passions of the mind increase the motion of the heart, as might be expected: but melancholy, when it makes men inactive, and uninfluenced by the impressions of objects, has a contrary effect, which is equally suitable to the foregoing theory.
Tenthly, In mortifications, also in the languid state that succeeds acute distempers, &c. the pulse sometimes intermits, suppose once in 5, 10, 20, &c. times, the interval being about double, and the strength of the pulse which succeeds the intermission about double also. Here the force of the heart seems to languish, and the time of contraction of the ventricle to be protracted, till a second contraction of the auricle intervenes, and protracts the ventricle’s contraction still farther, viz. to nearly twice the interval. The heart must therefore be surcharged, and contracting stronger from this respite, must send, as it were, a double quantity of blood into the aorta, i.e. make the pulse that succeeds much stronger. And this intermission may return at greater or less intervals, according to the circumstances, while this weakness of the heart continues: it may also remain, when once established, from habit, or association.
This intermission may perhaps rather be accounted for thus: in languid states the blood is accumulated in the beginning of the aorta. The aorta will not therefore receive much blood from the heart, though it does contract; i.e. no pulse will be felt; i.e. the interval will be double: the succeeding pulse will be strong, from the now greater emptiness of the aorta, and fulness of the heart: the intermission will also return when the accumulation in the aorta does. It agrees with this account, that these intermissions are usually felt in the region of the heart by the patients. May not intermissions arise from both causes in different circumstances?
Eleventhly, When the pulse flutters from flatulencies and spasms in the stomach and bowels, it appears that a sudden stop is put to the blood of the aorta, which by surcharging the left
