CHAP. XVIII.
Of the Circulation of the Blood.
FRom the Head, we are to look into the Thorax, and there to consider the Heart, and the Lungs. The Lungs, as most of the other Viscera, were believed to be of a Parenchymous Substance, till Malpighius found by his Glasses (s)(s) Epist. de Pulmonibus. that they consist of innumerable small Bladders, that open into each other, as far as the outermost; which are covered by the outer Membrane, that incloses the whole Body of the Lungs: And that the small Branches of the Wind-Pipe are all inserted into these Bladders; about every one of which the Veins and Arteries are entwined, in an unconceivable Number of Nets and Mazes; that so the inspired Air may press upon, or mix with, the Mass of Blood, in such small Parcels as the Ancients had no Notion of. The Wind-Pipe also it self is nourished by an Artery that creeps up the Back-side, and accompanies it in all its Branchings: Which was first found out by Frederic Ruysch, a Dutch Professor of Anatomy at Leyden, about Thirty Years ago.
But
