CHAP. II. Of the great Artery, or Trunk of the Aorta.
THE great Artery from whence all the Arteries of the Body, ex∣cept the Rough, and Pulmonary, pro∣ceed, very much exceeds all the rest of the Arteries in thickness and length of Course. Nevertheless in substance and largeness it is not much different from the great Pulmonary Artery, extended from the right Ventricle of the Heart into the Lungs, which is vulgarly though erroneously call'd the right Ar∣terious Vein.
I. Now it is requisite that the Aorta should have such a solid Sub∣stance, least the hot and spiritous Blood, forc'd into it from the very Furnace it self, should be dissipated; and large∣ness is moreover required, to the end it may contain a sufficient quantity of Blood to be distributed to all the other Arteries proceeding from it.
II. The Orifice of the Heart being laid open, it adheres continuous to the left Ventricle; at it's very rise being furnish'd with three remarkable Valves, fashion'd like a Sigma prominent from the Heart toward the outward Parts, and hindring the return of the Blood from the Artery into the Ventricle of the Heart.
Before it issues forth from the Peri∣cardium it emits from it's self the Coro∣nary Artery, sometimes single, some∣times double, encircling the Basis of the Heart like a Crown, and thence scattering branches the whole length of it, accompany'd with the Coronary Veins, with which some affirm it to be united by Anatomists, which however would be a very difficult thing to de∣monstrate.
Near the Orifice of this Coronary Artery stands a Valve, so order'd, that the Blood may easily flow back out of the great Artery into the Coro∣nary.
This will not admit a slender Bodkin thrust into it, from the Part next the Heart into the great Artery; but from the Part next the great Artery a Bod∣kin will easily enter the Coronary; by which means we find where the Valve