The twelve Pairs of Nerves that have their Beginning from between the _Vertebra's_ of the Back, are each of them divided into two Branches, as the others; and their Branches are distributed in like manner to the Muscles of the Breast, and to those of the Back and _Abdomen_. The five Pairs which take their Rise from between the _Vertebra's_ of the Loins, have thicker Branches than the others, and the distribution of them is made to the Muscles of the Loins, _Hypogastrium_, and Thighs. Of the six Pairs of Nerves that proceed from the _Os Sacrum_, the four Upper with the three Lower of the Loins, send forth Fibres of Nerves to the Thigh, Leg, and Foot; and the two last Pairs impart Nerves to the _Anus_, Bladder, and privy Parts. _What is the Structure of the Arteries?_ The Arteries are long and round Canals, consisting of four sorts of Tunicks or Membranes, which have their Rise from the left Ventricle of the Heart, from whence they receive the Blood, and convey it to all the Parts of the Body for their Nourishment. _What is the Construction of these four Tunicks or Membranes of the Arteries?_ {62} The first being thin and Nervous in its outward Superficies, is in the Inside a _Plexus_ or Interlacement of small Veins and Arteries, and Fibres of Nerves, which enter into the other following Tunicks, to nourish them. The second sticking close to the former, is altogether full of whitish Glandules, that serve to separate the serous Particles of the Blood. The third is intirely Musculous, and interwoven with Annular Fibres. The fourth is very thin, and hath its Fibres all streight. _Whence proceeds the Pulse or beating of the Arteries?_ It is deriv'd from the Heart, and exactly answers to its Motion of _Diastole_ and _Systole_. _By what Name is the first Trunk of the Arteries call'd, and what is the Effect of the Distribution made thence to the whole Body?_ The first Trunk of the Arteries is nam'd _Aorta_, or the _thick Artery_, which proceeds immediately from the left Ventricle of the Heart, whereto it communicates before its departure from the _Pericardium_, one or two small Branches call'd the _Coronary_: Afterward it is divided into two Branches, whereof one goes upward, and is term'd the _Ascending Artery_; and the other downward, under the Denomination of the _Descending Artery_. The _Ascending Artery_ ariseth upward along the _Aspera Arteria_ or Wind-Pipe, to the Clavicles, and is there divided into two Branches, call'd the _Subclavian Arteries_, one whereof goes forward to the Right side, and the other to the Left; and they both send forth on each side {63} divers Branches, which take their Names from the several Parts, whereto they are distributed; such are the _Carotides_ or _Soporales Interni & Externi_, which pass to the Head; the _Mediastina_; the _Intercostal_; the _Axillar_, and others.