The Fourth Figure

Shews after what manner the lateral Bosom goes into the Jugular Vein with a di∣verting place hanging to it.

• A. The lateral Bosom descending.
• B. That Bosom sliding into the Skull, and dilating it self into a large and round Cavity, for the receiving of which there is a peculiar Den formed in the outward part of the Skull.

• C. The aforesaid Cavity or diverting place, in which the blood, about to descend, may go aside, lest it should else rush too strongly upon the Jugular Vein; by which also care is taken, that the blood may not flow back or regurgitate out of the Jugular Vein into the Bosom.
• D. The beginning of the Jugular Vein.

But as the Carotides (of whose office and ascent we have hitherto spoken) carry the destinated Tribute of the blood to the Brain; so the Vertebrals serve chiefly for the watering the Cerebel and the hinder part of the oblong Marrow. Hence we observe, because the conformation of the Cerebel is alike in all Creatures, therefore also the Vertebral Arteries, different from the Carotides, are found alike in all without any great difference. Nor does there seem to be need of any great provision for the ad∣mission or entrance of the Vertebral Arteries within the Skull; because, as they car∣ry a lesser portion of the blood, and for that the blood it self that is to be bestowed on the Cerebel, is wont there to be agitated or moved with no perturbations of pas∣sions or conceptions; therefore there is not that necessity that there should be placed any remora or any incitement for its Torrent.

The Vertebral Artery, arising from the branch in the fifth Rib, in its whole ascent through the hinder part of the Head, passes through the little holes cut in the extube∣rances of the Vertebrae, till it comes near the Basis of the hinder part of the Head; where the same being bent down on either side, and admitted into the Skull by the last hole, excepting where the spinal Marrow goes forth, is carried by the side of the oblong marrow; but as soon as it is brought to the region of the Cerebel, it sends forth branches on either side, which cover its superficies, and besides on its back side make infoldings no less signal than those commonly called the Choroeides, and with larger Kernels more thickly interwoven. As those shoots convey the Juyce requisite for the stilling forth the animal Spirits, so these convey the heated blood and the puri∣fied from the serous Colluvies. Further, beneath the Cerebel, both the Vertebral branches, inclining mutually one to another, are united, as it were for that end, that if the flowing of the blood should be stopped on either side, it might be supplied from the other to the whole compass of the Cerebel and its neighbouring parts. These sanguiferous Vessels covering the Cerebel, even as the others do the Brain, make signal infoldings both in its outward superficies, and in that of the oblong marrow, and also within its lappets and folds; from which small shoots are sent forth every where into its under-lying substance: so that from these a subtil liquor, as it were stilled forth and imbibed by the Cortical substance of the Cerebel, seems to go into animal Spirits. By what means, and in what parts of the Head the production of the animal Spirits is performed, remains next to be inquired into.