[f] Arteria Carotis Aliquanto posterius in homine quàm in alio quovis animali, Calvariam ingreditur, scil. juxta illud foramen, per quod sinus lateralis in Venam jugularem desiturus cranio elabitur; nam in cæteris hæc arteria sub extremitate, seu processu acuto ossis petrosi, inter cranium emergit: verùm in capite humano, eadem, ambage longiori circumducta (ut sanguinis torrens, priusquam ad cerebri oram appellit, fracto impetu, leniùs & placidiùs fluat) prope specum ab ingressu sinûs lateralis factum, Calvariæ basin attingit;——& in majorem cautelam, tunicâ insuper ascititiâ crassiore investitur. And so he goes on to shew the Conveniency of this Guard the Artery hath, and its Passage to the Brain, and then saith, Si hujusmodi conformationis ratio inquiritur, facilè occurrit, in capite humano, ubi generosi affectus & magni animorum impetus ac ardores excitantur, sanguinis in Cerebri oras appulsum debere esse liberum & expeditum, &c. Atque hoc quidem respectu differt Homo à plerisque Brutis, quibus, Arteria in mille surculos divisa, ne sanguinem pleniore alveo, aut citatiore, quàm par est, cursu, ad cerebrum evehat, Plexus Retiformes constituit, quibus nempe efficitur, ut sanguis tardo admodum, lenique & æquabili fere stillicidio, in cerebrum illabatur. And then he goes on to give a farther Account of this Artery, and the Rete mirabile in divers Creatures. Willis, ibid. cap. 8.
[g] Galen thinks the Rete mirabile is for concocting and elaborating the Animal Spirits, as the Epididymides, [the Convolutions κιρσοειδοῦς ἕλικος] are for elaborating the Seed. De Us. Part. L. 9. c. 4. This Rete is much more conspicuous in Beasts than Man; and as Dr. Willis well judges, serves, 1. To bridle the too rapid Incursion of the Blood into the Brain of those Creatures, whose Heads hang down much. 2. To separate some of the superfluous serous Parts of the Blood, and send them to the Salival Glands, before the Blood enters the Brain of those Animals, whose Blood is naturally of a watery Constitution. 3. To obviate any Obstructions that may happen in the Arteries, by giving a free Passage through other Vessels, when some are stopped.
In Quadrupeds, as the Carotid Arteries are branched into the Rete Mirabile, for the bridling the too rapid Current of Blood into the Brain; so the Vertebral Arteries, are, near their Entrance into the Skull, bent into an acuter Angle than in Man, which is a wise Provision for the same Purpose.
CHAP. III.
Of the Necks of Quadrupeds.
From the Head pass we to the Neck, no principal Part of the Body, but yet a good Instance of the Creator’s Wisdom and Design, inasmuch as in Man it is short, agreeable to the Erection of his Body; but in the Four-footed Tribe it is long, answerable to the Length of the Legs[a], and in some of these long, and less strong, serving to carry the Mouth to the Ground; in others shorter, brawny and strong, serving to dig, and heave up great Burdens[].
But that which deserves especial Remark, is that peculiar Provision made in the Necks of all, or most granivorous Quadrupeds, for the perpetual holding down their Head in gathering their Food, by that strong, tendinous and insensible Aponeurosis, or Ligament[c] braced from the Head to the middle of the Back. By which means the Head, although heavy, may be long held down without any Labour, Pain, or Uneasiness to the Muscles of the Neck, that would otherwise be wearied by being so long put upon the Stretch.
FOOTNOTES:
[a] It is very remarkable, that in all the Species of Quadrupeds, this Equality holds, except only the Elephant; and that there should be a sufficient special Provision made for that Creature, by its Proboscis or Trunk. A Member so admirably contrived, so curiously wrought, and with so great Agility and Readiness, applied by that unwieldy Creature to all its several Occasions, that I take it to be a manifest Instance of the Creator’s Workmanship. See its Anatomy to Dr. A. Moulen’s Anat. of the Elephant, p. 33. As also in Mr. Blair’s Account in Phil. Trans. Nᵒ. 326.
Aliorum ea est humilitas ut cibum terrestrem rostris facilè contingant. Quæ autem altiora sunt, ut Anseres, ut Cygni, ut Grues, ut Cameli, adjuvantur proceritate collorum. Manus etiam data Elephantis, qui propter magnitudinem corporis difficiles aditus habebant ad pastum. Cic. de N. D. L. 2. c. 47.