The _Descending Artery_, before its departure from the Breast, affords certain Branches to the _Pericardium_, Diaphragm, and lower Ribs; afterward it penetrates the Diaphragm, and constitutes seven double Branches. The first is of those that are call'd _Coeliack_, and which go to the Liver and Spleen. The second Branch contains the _Upper Mesenterick_. The third the _Emulgent_, which pass to the Reins. The fourth the _Spermatick_, which are extended to the Genitals. The fifth the _Lower Mesenterick_. The sixth the _Lumbar_. And the seventh the _Muscular_. But assoon as the great Trunk is come downward to the _Os Sacrum_, it divides it self into two thick Arteries nam'd the _Iliack_, which are distributed on both sides, each of them making two Internal and External Branches, which likewise impart Sprigs or lesser Arteries, to the Bladder, _Anus_, _Matrix_, and other adjacent Parts: Then the Master-Branch forms the _Crural_ Arteries on the inside of the Thighs, which are communicated by multiplying their Number even to the ends of the Toes, in passing over the External Ancle-Bones of the Feet. _What is the Structure of the Veins?_ The Veins are long and round Canals made of four kinds of Tunicks or Membranes, whose Office it is to receive the Blood that remains after the Nourishment is taken, and to carry it back to the Heart to be reviv'd. {64} _What is the Form of the four Tunicks that make the Canals of the Veins?_ The first is a Contexture of Nervous and streight Fibres. The second is a _Plexus_ of small Vessels that carry the Nourishment. The third is all over beset with Glandules thro' which are filtrated the serous Particles of the Blood contain'd in the Vessels of the second Tunicle. The fourth is a Series of Annular and Musculous or Fleshy Fibres. _Which are the most numerous, the Arteries or the Veins?_ The Number of the Veins exceeds that of the Arteries; and there are scarce any Arteries without Veins accompanying them. _Where is the Beginning and Original of all the Veins?_ All the Veins have their Root in the Liver, and two of the three great Trunks that proceed from thence, are call'd _Vena Portæ_, and _Vena Cava_; and the third is twofold, _viz._ the _ascending_ and the _descending_. The _Vena Portæ_ is distributed to all the Parts contain'd in the lower Belly, and terminated in the Fundament; where it makes the Internal Hæmorrhoidal Veins. The _Vena Cava_ is immediately divided into two thick Branches, one whereof ariseth upward to the Right Ventricle of the Heart, and forms the _ascending Vena Cava_; as the other goes downward to the Feet, and constitutes the _descending_. _What is the Distribution of the ascending _Vena Cava_?_