Explain'd, &c. (continued 2)

The five Teguments being remov'd, we meet with as many Muscles on each side, viz. the descending Oblique, the ascending Oblique, the Transverse, the streight, and the Pyramidal, by the means whereof the Belly is extended and contracted. Afterwards appears a Membrane nam'd Peritonæum, which contains all the Bowels, and covers the whole lower Belly, being strongly fasten'd to the first and third Vertebra's of the Back. The Fat skinny Net which lies immediately under the Peritonæum, is call'd Epiploon and Omentum, or the Caul; it floats over the Bowels, keeping them in a continual Suppleness necessary for their Functions, maintains the Heat of the Stomach, and contributes to Digestion.

It remains to take an Account of the Bowels viz. the Stomach, Mesentery, Liver, Spleen, Kidneys, Bladder, and Guts, together with the Parts appointed for Generation, which in Men are the Spermatick Vessels, the Testicles, and the Penis; and in Women, the Spermatick Vessels, the Testicles or Ovaries, the Matrix, and its Vagina or Neck.

What is the Stomach?

It is the Receptacle of the Aliments or Food convey'd thither thro' the Oesophagus or Gullet, which is a Canal, or kind of streight Gut that reacheth from the Throat to the Mouth of the Stomach. The Stomach it self is situated immediately under the Diaphragm or Midriff, between the Liver and the Spleen, having two Orifices, whereof the Left is properly call'd Stomachus, or the Upper, and the Right (at its other Extremity) Pylorus, or the lower Orifice. Its Figure resembleth that of a Bag-Pipe, and the greater part of its Body lies toward the Left side. It is compos'd of three Membranes, viz. one Common, which it receives from the Peritonæum; and two Proper; the two uppermost being smooth, and the innermost altogether wrinkled.

What is the Pancreas or Sweet-bread?

It is a Fat Body, consisting of many Glandules wrapt up in the same Tunicle, being situated under the Pylorus or lower Orifice of the Stomach: It helps Digestion, and hath divers other uses; but its principal Office is to separate the serous Particles of the Blood, to be convey'd afterward into the Gut Duodenum, by a Canal or Passage, nam'd the Pancreatick. This Juice serves to cause the Chyle to ferment with the Choler, in order to remove the grosser Particles from those that ought to enter into the Lacteal Vessels.

Into how many sorts are the Guts distinguish'd?

There are two sorts, viz. the thin and the thick.

How many thin or small Guts are there?

Three; that is to say, the Duodenum, the Jejunum, and the Ileon.

How many thick Guts are there?

Three likewise; viz. the Cœcum, the Colon, and the Rectum.

Why are some of them call'd thin Guts, and others thick?

Because the thin are smaller, being appointed only to transport the Chyle out of the Stomach into the Reserver; whereas the thick are more large and stronger, serving to carry forth the gross Excrements out of the Belly.

Are the six Guts of an equal length?

No, the Duodenum, which is the first of the thin Guts, is only twelve Fingers breadth long. The Jejunum, being the second, so call'd because always empty, is five Foot long: The third is nam'd Ileon, by reason of its great Turnings which oblige it to pass to the Os Ilion, where it produceth a Rupture; it extends it self almost twenty Foot in length.

The first of the thick Guts, known by the Name of Cœcum, is very short, and properly only an Appendix or Bag of a Finger's length. That which follows is the Colon, being the largest of all, and full of little Cells, which are fill'd sometimes with Wind and other Matters that excite the Pains of the Colick. It encompasseth the thin Guts, in passing from the top to the bottom of the Belly, by the means of its great Circumvolutions, and is from eight to nine Foot long. The last is the Rectum or streight Gut, so nam'd, because it goes directly to the Fundament: It is no longer than ones Hand, but it is fleshy, and situated upon the Os Sacrum, and the Coccyx or Rump-Bone.

What is the Peristaltick Motion of the Guts?

It is the successive Motion and Undulation, whereby the Guts insensibly push forward from the top to the bottom, the Matters contain'd in them; and that Motion which on the contrary is perform'd from the bottom to the top, is term'd the Antiperistaltick as it happens in the Iliack Passion, or twisting of the Guts, call'd Domine Miserere, by reason of its intolerable Pain.

What is the Mesentery?

It is a kind of Membrane somewhat fleshy, which is join'd to the Spine in the bottom and middle of the Belly, and by its folding, keeps all the Guts steady in their place; it is all over beset with red, white, and Lymphatick Vessels; that is to say, those that carry the Blood, Chyle, and Lympha, which serves to cause this last to run more freely, and to ferment. Three notable Glandules are also observ'd therein, the greatest whereof lies in the middle, and is nam'd Asellius's Pancreas; the two other lesser are call'd Lumbar Glandules, as being situated near the Left Kidney. From each of these Glandules proceeds a small Branch; and both are united together to make the great Lacteal Vein, or Thoracick Canal. This Tube conveys the Chyle along the Vertebra's of the Back to the Left Subclavian Vein; from whence it passeth into the ascending Vena Cava, and descends in the Right Ventricle of the Heart, where it assumes the form of Blood; from whence it passeth to the Lungs thro' the Pulmonary Artery; then it returns to the Heart thro' the Pulmonary Vein, and goes forth again thro' the Left Ventricle of the Heart, between the Aorta or great Artery, to be afterward distributed to all the Parts of the Body. This is the ordinary Passage for the Circulation of the Chyle, and the Sanguification of the Heart.

What is the Liver?

The Liver, being the thickest of all the Bowels, is plac'd in the Right Hypochondrium, at the distance only of a Fingers breadth from the Diaphragm; its Figure much resembling that of a thick piece of Beef: It is Convex on the outside, and Concave within; its Substance is soft and tender, its Colour and Consistence being like coagulated Blood: It is cleft at bottom, and divided into two Lobes, viz. one greater, and the other less: Its Office is to purifie the Mass of Blood by Filtration; and it is bound by two strong Ligaments, the first whereof adheres to the Diaphragm, and the second to the Xiphoides or Sword-like Cartilage. Two great Veins take their Rise from hence, viz. the Vena Portæ, and the Vena Cava, which form innumerable Branches, as it were Roots in the Body of the Liver. The Gall-Bladder is fasten'd to the hollow part thereof, and dischargeth its Choler into the Gut Duodenum, thro' the Vessels that bear the Name of Meatus Choledochi, or Ductus Biliares. This Choler is not a meer Excrement, but on the contrary of singular Use in causing the Fermentation of the Chyle, and bringing it to perfection.

What is the Spleen?

The Spleen is a Bowel resembling a Hart's Tongue in shape, and situated in the Left Hypochondrium, over-against the Liver: Its length is about half a Foot, and its breadth equal to that of three Fingers; its Substance being soft, as that of the Liver, and its Colour like dark coagulated Blood: It is fasten'd to the Peritonæum, Left Kidney, Diaphragm, and to the Caul on the inside; as also to the Stomach by certain Veins, call'd Vasa Brevia; nevertheless these Ligatures do not hinder it from wandering here and there in the lower Belly, where it often changeth its place, and causeth many dreadful symptoms by its irregular Motions. Its Office is to Subtilize the Blood by cleansing and refining it.

What are the Reins?

The Reins or Kidneys are Parts of a Fleshy Consistence, harder and more firm than that of the Liver and Spleen: They are both situated in the sides of the Umbilical Region, upon the Muscle Psoas, between the two Tunicks of the Peritonæum; but the Right is lower than the Left: Their Shape resembleth that of a French Bean, and they receive Nerves from the Stomach, whence Vomitings are frequently occasion'd in the Nephritical Colicks: They are fasten'd to the Midriff, Loins, and Aorta, by the Emulgent Arteries; as also to the Bladder by the Ureters. The Right Kidney likewise adheres to the Gut Cæcum, and the Left to the Colon. Their Office is to filtrate or strain the Urine in the Pelves or Basons, which they have in the middle of their Body on the inside, and to cause it to run thro' the Vessels call'd Ureters into the Bladder.

Immediately above the Reins on each side, is a flat and soft Glandule, of the thickness of a Nut; they are nam'd Renal Glandules, or Capsulæ Atribiliariæ, because they contain a blackish Liquor, which (as they say) serves as it were Leaven for the Blood, to set it a fermenting.

What is the Bladder?

It is the Bason or Reserver of Urines, of a Membranous Substance as the Stomach, being plac'd in the middle of the Hypogastrick Region; so that it is guarded by the Os Sacrum behind, and by the Os Pubis before: Two Parts are to be distinguish'd therein, viz. its Bottom and Top; by its Membranous Bottom it is join'd to the Navel, and suspended by the means of the Urachus, and the two Umbilical Arteries which degenerate into Ligaments in adult Persons: As by its fleshy Neck, longer and crooked in Men, and shorter and streight in Women it cleaves to the Intestinum Rectum in the former, and to the Neck of the Womb in the latter. Lastly, its Office is to receive the Urines to keep them, and to discharge them from time to time.

What are the Genitals in Men?

They are the Spermatick Vessels, the Testicles, and the Penis. The Spermatick Vessels are a Vein and an Artery on each side; the former proceeding from the Aorta, or thick Artery of the Heart; and the other from the Branches of the Vena Cava of the Liver. These Arteries and Veins are terminated in the Body of the Testicles, which are two in Number, enclos'd within the Scrotum.

The Office of the Testicles is to filtrate the Seed, which is brought thither from all the parts of the Body, thro' the Spermatick Vessels, called Præparantia, and afterwards to cause it to pass thro' others nam'd Deferentia, to the Vesiculæ Seminales, from whence it is forc'd into the Ureter, thro' two small and very short Canals.

The Penis or Yard is a Nervous and Membranous Part, well furnish'd with Veins and Arteries, containing in the middle the Canal of the Ureter: Its Extremity, which consists of a very delicate and spongy sort of Flesh, is call'd Balanus, or Glans, and the Nut, the Skin that covers it being nam'd the Præputium, or the Fore-Skin. Thus by the means of this swell'd Part, and stiff thro' the affluence of the Spirits, the Male injects his Seed into the Matrix of the Female, to propagate his Kind.

What are the Parts appropriated to Generation in Women?

They are the Spermatick Vessels, the Ovaries or Testicles, and the Matrix. The Spermatick Vessels are a Vein and an Artery on each side, as in Men: The Ovaries or Testicles, situated on the side of the bottom of the Matrix, are almost of the same bigness with those of Men, but of a round and flat Figure. The Vesiculæ, or little Bladders which they contain, are usually term'd Ova or Eggs by Modern Anatomists; and the Vessels that pass from these Testicles or Ovaries to the Cornua of the Uterus, are call'd Deferentia or Ejaculatoria.

The Matrix, Uterus or Womb, is the principal Organ of Generation, and the place where it is perform'd, resembling the Figure of a Pear with its Head upward, and being situated between the Gut Rectum and the Bladder: It is of a fleshy and membranous Substance, retain'd in its place by four Ligaments, fasten'd to the bottom; whereof the two upper are large ones, proceeding from the Loins, and the two lower round, taking their Rise from the Groin, where they form a kind of Goose-Foot, which is extended to the Os Pubis, and the flat part of the Thighs; which is the cause that Women are in danger of Miscarrying when they fall upon their Knees.

The Exterior Neck of the Womb, call'd Vagina, is made almost in form of a Throat or Gullet, extending it self outwardly to the sides of the Lips of the Pudendum, and being terminated inwardly at the internal Orifice of the Matrix, the shape whereof resembleth that of the Muzzle or Nose of a little Dog. The outward Neck of the womb is fasten'd to the Bladder and the Os Pubis before, and in the hinder part to the Os Sacrum: Between the Lips of the Pudendum lie the Nymphæ, which are plac'd at the Extremity of the Canal of the Bladder, to convey the Urines; and somewhat farther appear four Caruncles, or small pieces of Flesh, at the Entrance of the Vagina, which when join'd together make the thin Membrane call'd Hymen.

C H A P. XIV.

Of the Anatomy of the Thorax, Breast, or middle Venter.

What is the Breast?

It is a Cavity in which the Heart and the Lungs are principally enclos'd.

What is to be consider'd outwardly in the Breast?

Its extent, and the situation of the Parts therein contain'd.

What is its extent?

It is extended from the Clavicles to the Xiphoides, or Sword-like Cartilage on the fore-part, and bounded on the hinder by the twelfth Vertebra of the Back, having all the Ribs to form its Circumference, and the Diaphragm for its Bounds at bottom, separating it from the Abdomen or lower Belly.

What is the situation of the Parts contain'd in the Breast?

The Lungs take up the upper Region, and fill almost the whole Space, descending at the distance of two Fingers breadth from the Diaphragm; the Heart is situated in the middle, bearing its Point somewhat towards the Left side, under the Lobes of the Lungs, which are divided by the Mediastinum that distinguishes them into the Right and Left Parts.

How is the Breast Anatomiz'd or open'd?

After the dissection of the five Teguments, and the removal of the Muscles, as in the lower Belly, the Anatomist proceeds to lift up the Sternum or Breast-Bone, by separating it from the Ribs; then it is laid upon the Face, or else entirely taken away, to the end that the internal Parts of the Breast may be more clearly discover'd; whereupon immediately appear, the Heart, the Lungs, the Diaphragm, and the Mediastinum, which sticks to the Sternum throughout its whole length.

What is the Heart?

It is a most noble Part, being the Fountain of Life, and the first Original of the Motion of all the others; on which account it is call'd Primus vivens, & ultimum moriens; that is to say, the first Member that begins to live, and the last that dies.

What Parts are to be consider'd in the Heart?

Its fleshy Substance, with all its Fibres turn'd round like the Skrews of a Vice; its Basis, Point, Auricles, Ventricles, large Vessels, Pericardium and Ligatures or Tyes: The Basis is the uppermost and broadest part; the Point is the lowermost and narrowest part; the two Auricles or small Ears being as it were little Cisterns or Reservers, that pour the Blood by degrees into the Heart, are situated on each side above the Ventricles. The Ventricles, which are likewise two in Number, are certain Cavities in its Right and Left Sides. The large Vessels are the Aorta or great Artery, and the Vena Cava together with the Pulmonary Artery and Vein. The Pericardium is a kind of Bag fill'd with Water, wherein the Heart is kept; which is fasten'd to the Mediastinum by its Basis, and to the large Vessels that enter and go out of its Ventricles.

What are the Terms appropriated to the continual beating of the Heart?

They are Diastole and Systole, from whence proceed two several Motions, the first whereof is that of Dilatation, and the other of Contraction, communicated to all the Arteries which have the same Pulse.

To what use serves the Water contain'd in the Pericardium?

It prevents the drying of the Heart by its perpetual Motion.

What are the Lungs?

They are an Organ serving for Respiration, of a soft Substance, and porous as a Sponge, being all over beset with Arteries, Veins, Nerves, and Lymphatick Vessels, and perforated with small Cartilaginous Tubes, that are imparted to it from the Wind-Pipe, and are call'd Bronchia. Their Natural Colour is a pale Red, and marbl'd dark Brown; and their whole Body is wrapt up in a fine smooth Membrane, which they receive from the Pleuron. They are suspended by the Wind-Pipe, by their proper Artery and Vein, and by the Ligatures that fasten them to the Sternum, Mediastinum, and frequently to the Pleuron it self: They are also divided into the Right and Left Parts by the Mediastinum; having four or five Lobes, whereof those on the Left side cover the Heart. Their continual Motion consists in Inspiration, to take in the Air, and Expiration, to drive it out. The Larynx makes the Entrance of the Wind-Pipe into the Lungs, and the Pharynx that of the Oesophagus or Gullet, at the bottom of the Mouth to pass into the Stomach.

C H A P. XV.

Of the Anatomy of the Head, or upper Venter.

What is the head?

It is a bony Part, that contains and encloseth the Brain within its Cavity.

What is most remarkable in the outward parts of the Head?

The Temporal Arteries, the Crotaphitæ, or Temporal Muscles, and the Sutures of the Skull.

Why are these things considerable?

The Temporal Arteries are of good Note, because they are expos'd on the outside, lying even with the Skin. The Crotophite Muscles are so likewise, in regard that they cannot be hurt without danger of Convulsions, by reason of the Pericranium with which they are cover'd. And the Sutures, because the Meninges of the Brain proceed from thence to form the Pericranium.

What is the Pericranium?

It is a Membrane that lies under the thick hairy Skin of the Head, and immediately covers the Skull.

What are the Meninges?

They are two Membranes that enclose the Substance or Marrow of the Brain.

What is a Suture?

It is a kind of thick Seam or Stitch, that serves to unite the Bones of the Skull.

How many sorts of Sutures are there?

There are two sorts, viz. the true, and the false or Bastard.

What are the true Sutures?

They are three in number, namely the Sagittal, the Coronal, and the Lambdoidal.

What is the disposition or situation of the true Sutures?

The Sagittal is streight, beginning in the middle of the Fore-head, and sometimes at the root of the Nose, and being terminated behind, at the joining of the two Branches of the Lambdoidal Suture.

The Coronal appears in form of a Crown, passing to the middle of the Head, and descending thro' the Temples, to finish its Circumference in the Root of the Nose.

The Lambdoidal Suture is made like an open Pair of Compasses, the Legs whereof are extended toward the Shoulders; and the Button is in the top of the Head backward.

What are the Bastard Sutures?

They are those that are call'd Squamous or scaly.

What is the disposition of natural situation of these false Sutures?

They are plac'd at the two sides of the Head, and make a Semi-Circle of the bigness of the Ears, round the same Ears.

What difference is there between the true and spurious Sutures.

The true Sutures are made in form of the Teeth of a Saw, which enter one into the other; and the false or Bastard ones are those that resemble the Scales of Fishes, which are join'd together by passing one over the other.

What is the Use of the Sutures?

The Ancients were of Opinion, that they were made to hinder the Fracture of one Skull-Bone from passing thro' the whole Head; but there is more reason to believe that they have the three following Uses, that is to say, 1. To promote the transpiration of the Brain. 2. To give Passage to the Vessels that go to the Diploe. 3. To retain the Meninges, and to support the Mass of the Brain, which is cover'd by them.

What are the Names of the Bones that compose the Skull?

The Bone of the fore-part of the Head is call'd Sinciput, or the Fore-head-Bone, as also the Frontal or Coronal Bone. The Bone of the hinder-part, enclos'd within the Lambdoidal Suture, is term'd the Occipital. The two Bones that form the upper-part, and are distinguish'd by the Sagittal Suture, bear the Name of Parietals, one being on the Right side, and the other on the Left. And those behind the Ears are call'd Temporal, Squamosa, or Petrosa. These also are distinguish'd into the Right and Left Temporals, and are join'd to the bottom of the Parietal by a bastard squamous Suture.

What is most remarkable in the thickness of the Skull-Bones?

The Diploe, which is nothing else but a Plexus or Contexture of small Vessels, that nourish the Bones, and in the middle of their thickness make the distinction of the first and second Tablature of the Bones; whence it sometimes happens that an exfoliative Trepan, or Semi-Trepan, is sufficient, when the first of these two Tables is only broken, the other remaining entire.

Is the Brain which is preserv'd in the Skull all of one Piece, or one equal Mass?

No, it is distinguish'd by the means of the Meninges into the Brain it self, and the Cerebellum or little Brain; the Brain, properly so called, takes up almost the whole Cavity of the Skull, and the Cerebellum is lodg'd altogether in the hinder-part, where it constitutes only one entire Body; whereas the former is divided into the Right and Left Parts by the Meninges, which cut it even to the bottom; whence these Foldings are call'd Falx; i. e. a Scythe or Sickle.

What is chiefly remarkable in the Substance of the Brain?

The Ventricles or Cavities which are found therein, together with the great Number of Veins, Arteries, Lymphatic Vessels, and Nerves, that carry Sense to all the Parts of the Body, and Spirits for their Motion.

An exact Historical Account of all the Holes of the Skull, and the Vessels that pass thro' them.

To attain to an exact Knowledge of all the Holes with which the inside of the Basis of the Skull is perforated, they are to be consider'd either with respect to the Nerves, or to the Sanguinary Vessels.

There are nine Pairs of Nerves that arise from the Medulla Oblongata, and go forth out of the Skull through many Holes hereafter nam'd.

The first Pair is that of the Olfactory Nerves, appropriated to the Sense of Smelling, which are divided below the Os Cribiforme, or Sieve-like Bone, into divers Threads, that passing into the Nose through many Holes with which this Bone is pierc'd, are distributed to the inner Tunick of the Nose.

The second Pair is that of the Optick or Visual Nerves, that pass into the Orbits of the Eyes, thro' certain peculiar Holes made in the Os Sphenoides, or Wedge-like Bone, immediately above the Anterior Apophysis Clinoides.

In the Portion of the Os Sphenoides, that makes the Basis of the Orbit, lies a Fissure about seven or eight Hairs breadth long, which is to be observ'd chiefly at the bottom, that is to say, below the Hole, thro' which the Optick Nerve passeth; where it is almost round, and larger than at the top, where it is terminated in a very long and acute Angle.

There are many Pairs of Nerves that enter into the Orbit thro' this Fissure, viz. 1. The third Pair, call'd the Motorii Oculorum. 2. The fourth Pair, nam'd Pathetici, by Dr. Willis. And 3. The whole sixth Pair. Besides these three Pairs, which go entire thro' this Cleft, there is also a Passage for the upper Branch of the foremost Fibre of the fifth Pair, which the same renowned Physician calls the Ophthalmick Branch. Beyond the lower-part of the said Fissure, toward the hinder-part of the Head, is to be seen in the Os Sphenoides on each side, a Hole that doth not penetrate the Basis of the Skull, but makes a kind of Ductus, about an Hair's breadth long, which is open'd behind the Orbit on the top of the Space between the Apophysis Pterygoides, and the third Bone of the Jaw; thro' this Ductus runs the lower Branch of the foremost Fibre of the fifth Pair.

About the length of two Hairs breadth beyond these Ductus's, we may also discover in the Os Sphenoides, or Wedge-like Bone, two Holes of an Oblong and almost Oval Figure, which are plac'd in the hindermost sides of that of the Os Sphenoides, and gives passage to the hindermost Fibre of the fifth Pair.

The Hole thro' which runs the Auditory Nerve, that makes the seventh Pair, is in the middle of the hinder-part of the Os Petrosum, that looks toward the Cerebellum: This Hole being very large, is the Entrance of a Ductus that is hollow'd in the Os Petrosum, and which sinking obliquely from the fore-part backward, for the depth of about two Hairs breadth, forms as it were the bottom of a Sack, the lowermost part whereof is terminated partly by the Basis of the Cochlea, and partly by a Portion of the Mouth of the Vestibulum. At the bottom of this Ductus are many Holes, but the most considerable is that of the upper-part, thro' which passeth a Portion of the Auditory Nerve. This is also the Entrance of another Ductus made in the Os Petrosum, which is open'd between the Apophysis Mastoides and Styloides: These other Holes afford a Passage to the Branches of the soft Portion of the same Auditory Nerve.

Below this Ductus there is a remarkable Hole form'd by the meeting of two hollow Cuts the larger whereof is in the Occipital Bone and the other in the lower-part of the Apophysis Petrosi: From the middle of the upper-part of this Hole issueth forth a small Prominence or bony Point, whereto is join'd an Appendix of the Dura Mater, which divides the Hole into two parts; so that thro' the foremost Orifice passeth the Nerve of the eighth Pair, and that which is call'd the Spinal Nerve. We shall have occasion hereafter to shew the Use of the hinder Orifice.

Near the great Hole of the Occipital Bone from whence proceeds the Medulla Oblongata, we may observe a Hole almost round and oblong thro' which passeth the Nerve of the ninth Pair. This Hole is entirely situated in the Occipital Bone, and making a little Way in the Bone passeth obliquely from the back-part forward. In the inside of the Skull this Hole is sometimes double, but its two Entrances are re-united in the outward-part of the Skull; and the two Branches that form the Origine of this Nerve and which pass thro' these two Holes, are likewise re-united at their Departure, These are the Passages of the nine Pairs of Nerves that proceed from the Medulla Oblongata, and it remains only to show that Paths thro' which the Intercostal Nerve goes forth, as also that of the tenth Pair. The Intercostal runs out of the Skull thro' the Ductus that gives Entrance to the Internal Carotick Artery. As for the tenth Pair, in regard that it ariseth from the Marrow which is enclos'd between the Occipital Bone and the first Vertebra, it goes forth thro' the Hole of the Dura Mater, where the Vertebral Artery enters.

To know well the Holes thro' which the Vessels that belong to the inner-part of the Head enter, and issue forth, it is requisite to distinguish them into those which are distributed to the Dura Mater, and those that are appointed for the Brain. The Vessels of the Dura Mater, are Branches of the Carotick or Vertebral Arteries.

In the Os Sphenoides, or Wedge-like Bone, behind the Hole thro' which passeth the hindermost Fibre of the fifth Pair of Nerves lies another small Hole, almost round, that gives Entrance to a Branch of the External Carotick Artery, which in entring, immediately adheres to the Dura Mater, and forms many Ramifications to overspread the whole Portion of this Membrane, which covers the sides, and the upper-part of the Brain.

At the bottom and top of the lateral outward part of the Orbit of the Eye, above the acute Angle, for want of the Os Sphenoides, there is a Hole thro' which passeth an Artery, being a Twig of a Branch of the Internal Carotick, which is diffus'd in the Eye, and distributed to almost the whole Portion of the Dura Mater, that covers the fore-part of the Brain.

The Vertebral Artery in entring into the Skull, furnisheth it on each side with a considerable Branch, which is dispers'd throughout the whole Portion of the Dura Mater that covers the Cerebellum.

As for the Veins that accompany these Arteries, they almost all go out of the Skull thro' the same Holes where the other enters.

There are four thick Arteries which convey to the Brain the Matter with which it is nourish'd, and that whereof the Spirits are form'd, viz. the two Internal Caroticks, and the two Vertebrals.

The Internal Carotick Arteries enter into the Skull thro a particular Ductus made in the Temporal Bone, the Mouth thereof being of an Oval Figure and situated in the outward part of the Basis of the Skull, before the Hole of the Internal Jugular. This Ductus extends it self obliquely from the back-side forward, and after having made about three Hairs breadth in length, is terminated in the hinder-part of the Os Sphenoides. The Artery traverseth the whole winding Compass of this Ductus, which resembles the Figure of the Roman Letter S, and at the Mouth of the same Ductus runs under the Dura Mater along the sides of the Os Sphenoides to the Anterior Apophyses Clinoides, where it riseth up again, to perforate the Dura Mater, and to adhere to the Root of the Brain. These Vessels, in like manner, after their departure from the Bone of the Temples to the place where they pierce the Dura Mater, make a second Circuit in form of the Roman Character S. At the place where these Carotick Arteries penetrate the Dura Mater, they send forth a thick Branch, which enters into the Orbit of the Eye, by the lower-part of the Hole, thro' which the Optick Nerve hath its Passage.

The Vertebral Arteries proceeding from the Holes of the transverse Apophyses of the first Vertebra, turn about in passing under the upper oblique Apophyses of the seven Vertebra's: Afterward they perforate the Dura Mater, and running under the Marrow, enter into the Skull thro' the Occipital Hole; then inclining one toward another, they are re-united, and form only one single Trunk.

The Veins that bring back the Blood from the Substance of the Brain, are emptied into the Sinus's of the Dura Mater, which are all discharg'd into those that are call'd Lateral, which last go out of the Skull immediately under the Nerves of the eighth Pair, thro' the hinder-part of the Hole made by the meeting of the Occipital Bone, and the Apophysis Petrosa. These Lateral Sinus's fall into the Internal Jugulars, which are receiv'd into a considerable Sinking hollow'd on each side in the outward, part of the Basis of the Skull, which is nam'd the Pit or Hole of the Internal Jugular.

In the upper and hinder-part of the Hole, from whence the lateral Sinus's issue forth, is to be seen an opening in the Extremity of a Ductus, the Mouth whereof lies behind the Condyli, which are on the sides of the Occipital Trunk: This Ductus is extended about the length of two Hairs breadth in the Bone, and the Canal enclos'd therein is open'd immediately into the Vertebral Sinus: So that one might affirm it to be as it were its Original Source. Whence it appears that the Blood contained in the lateral Sinus's is emptied thro' two places; the greater Portion thereof descending in the Jugulars from the Neck, and the other in the Vertebral Sinus's: Sometimes those Ductus's are four only on one side, another while both are stopt up, and the Blood contain'd in the lateral Sinus's is discharg'd into the Internal Jugulars.

Behind the Apophysis Mastoides on each side is a remarkable Hole, thro' which passeth a thick Vein, which brings back part of the Blood that hath been distributed to the Teguments and Muscles, which cover part of the Occiput or hinder-side of the Head: This Vein is open'd into the lateral Sinus's at the place where they begin to turn about. But in the Heads of some Persons, this Hole is found only on one side, and even sometimes not at all, in which case the Blood contain'd in the Vessels falls into the External Jugulars, with which the Branches of this Vein have a Communication.

In each Parietal Bone on the side of the Sagittal Suture, at a little distance from the Lambdoidal, appears a Hole, thro' which passeth a Vein, that brings back the Blood of the Teguments of the Head, and dischargeth it self into the upper Longitudinal Sinus. These Holes are sometimes on both; and then the Blood contain'd in the Branches of this Vein runs into the External Jugulars.

In the middle of the Sella of the Os Sphenoides, we may observe one or two small Holes thro' which (according to the Opinion of some Modern Anatomists) the Lympha contain'd in the Glandula Pituitaria is thrown into the Sinus of the edge of the Os Sphenoides; nevertheless it is certain, that these Holes are fill'd only with Sanguinary Vessels, which carry and bring back the Blood of the Bones and Membranes, whereof those Sinus's are compos'd; besides that, these Holes are rarely found in adult Persons.

Between the Spine of the Coronal Suture and the Crista Galli, is a Hole which serves as an Entrance for a Ductus, which sinks from the top to the bottom, the length of about two Hairs breadth in the thickness of the inner Table of the Coronal: The Root of the upper Longitudinal Sinus is strongly implanted in this Hole, which also affords a Passage to some Sanguinary Vessels appointed for the Nourishment of this inner Table.

Many other small Holes are found in divers places of the Basis of the Skull; the chief whereof are those that are observ'd in the Apophysis Petrosa, and give Passage to a great number of Vessels that serve for the Nutriment of that part of the Temporal Bone which is call'd the Tympanum, or Drum: The other Holes are principally design'd for the Vessels that are serviceable in the nourishing of divers parts of the Basis of the Skull.

After what manner is the opening of the Head or Skull perform'd?

It is done by sawing it asunder round about and above the Ears; then it is taken off, after having before cut off the Hair, and made a Crucial Incision in the Skin from the fore-part to the hinder, and from one Ear to the other; as also after having pull'd off and laid down the four Corners to the bottom.

How is the Brain anatomiz'd?

It is done by cutting it Superficially, and by Leaves, in order to discover by little and little the Ventricles, Vessels, and Nerves, with their Original Sources, &c. Or else it is taken entire out of the Skull, (the Nerves having been before examin'd) and laid down; so that without cutting any thing, all the parts of the Brain may be set in their proper places, to find out those that are sought for.

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