CHAP. IV.
Of the Natural Cure.
IN order to shew how persons recover out of a fit of this Disease, by the mere efforts of nature, I shall beg leave to premise a few of the most probable opinions, and best establish’d propositions, concerning Animal Motion, which I shall here take for granted, and refer the reader, for a physical demonstration of them, to the ingenious Essays of Doctors Porterfield, Whytt, Simson, and Haller.
Animal and Muscular Motion is said to be of two kinds, viz. Voluntary, and Involuntary or Habitual.
By Voluntary Motion is meant the action of any Muscle or Muscles produc’d by an immediate or conscious determination of the Mind; of this kind are the several occasional motions of the Body.
Involuntary or Habitual Motions are such as proceed originally from the Mind also, but are so establish’d, by long custom, that the Mind is not immediately conscious of them, nor can stop them at pleasure[13]. To this class, the Motion of the Heart, the peristaltic Motion of the Stomach and Guts, Respiration, and several Motions of the Eyes belong.
The vital Motions are suppos’d to be continued by a stimulus constantly applied to the Fibres of the Muscles which perform them.
Hence the Ventricles of the Heart are constantly irritated and stretch’d by the Venous Blood, which brings them into contraction, to propel the Blood through the Body.