ner of thin Plates, or Lamella, between which run a great Number of Veffels carrying Fluids proper for Moisture and Nourishment; which all together constitute or make up the white, hard, friable and elastic Subftance call'd a Cartilage. (5.) Since the largest Artery hath the greatest Pulfa- Their fifth and tion, and this being in the Middle of the Bone, laft State of a it will there first become a Cartilage, which by perfect Bone. Degrees becomes harder and more compact, till at last it is perfectly offified, or arriv'd to the proper Confistence of a Bone; and the Blood-Veffels being now comprefs'd on all Sides, bring no more Blood than what is fufficient to fupply the Place of the decaying Particles; they having now obtain'd their utmost Extent, Hardness, and Solidity. And hence, fince Bones begin to offify Why Bones are in the middle Parts firft, 'tis easy to understand hardest and Smallest they will of Confequence be there both hardest and fmalleft; while on the contrary they will be more extended towards the Extremities, and of a more foft and cartilaginous Nature. Thus much for Ofteogeny.

in the Middle.

OSTEOGRAPHY in the next Place Ofteography. teaches the Fabric of the Bones, or the Structure and Compages of a Sceleton.

A SCELETON then is a Syftem of Bones A Sceleton, clear'd of the Flesh, and join'd together in the what. fame Manner as they exifted in the Body. In order to understand this aright, it will be neceffary to mention the feveral Affections of a Bone, and the Manner of their Articulations.

THE Affections of a Bone, which I fhall here Affections of obferve, are of two Sorts, viz. Cavities and Pro- the Bones. minencies. The Cavities of Bones are deep or fhallow. A deep Cavity is call'd Cotyle; but the Cotyle. fuperficial one is call'd Glene. The Prominencies Glene. of a Bone are of two Kinds, viz, (1.) An Apo- Apophyfis. phyfis, which is a Protuberance made by the Fi

Gg 4

bres

Epiphyfis.

bres of a Bone. (2.) An Epiphyfis, which is only a fmall Bone fet upon the Extremity of a bigger Bone, which in time unite in one. Both the one and the other are ufually upon the Extremities of the Bones; and ferve either for the Infertion of Muscles, or the Articulation of the Bones. If the Protuberance be large and round, it is call'd Caput, or the Head; if fmall and round, it is call'd Condylus; if fharp, Corone, Styloides, &c. THE ARTICULATION of the Bones are tion of Bones. of the following Kinds. (1.) Diartbrofts, where there is a manifeft Motion. (2.) Synchondrofis, which is by means of a Cartilage, and with a fmall and obfcure Motion. (3.) Synarthrofis, without any Motion at all.

Condylus.
Corone.

The Articula

Diartbrofis.

DIARTHROSIS is again of three Sorts: (1.) Enarthrodia. Enarthrofis; which is when a large round Head of a Bone is receiv'd into a large Cavity; as of Arthrodia. the Thigh-Bone in the Ifchium. (2.) Arthrodia, which is when a flat plane Head of a Bone is receiv'd into a fhallow Cavity; as the Articulation of the Humerus with the Scapula. (3.) Ginglymus, which is when the Bones articulated mutually receive and are receiv'd by each other: As in that of the Humerus and Cubit.

Ginglymus.

Synchondrofis.

Synarthrofis.
Harmonia.

Sutura.

SYNCHONDROSIS is when the Extremities of two Bones are join'd together by means of an intervening Cartilage, as in the Vertebre, and the Ribs and Sternum; where though the Motion of all is manifeft, yet that of any two is fcarce perceptible.

SYNARTHROSIS is alfo of three Sorts. (1.) Harmonia, which is by a fimple Contact of the Extremities of Bones, without any mutual Ingrefs, and is defign'd by a right or oblique Line. (2.) Sutura, which is when two Bones are mutually indented into each other, and lock like the Teeth of a Saw; as in the Articulations

of

of the Bones of the Scull. (3.) Gomphofis is Gomphofis. when a Bone is faften'd or focketed into another; as the Teeth in the Jaw-Bones.

IN the SCELETON we shall take a View of the Bones in the following Order, viz. Of the Scull, the Spine, the Thorax, the Pelvis, the Arms and the Legs.

THE Bones of the Scull or Cranium are Six, viz. Of the Bones (1.) The Os Frontis or Forehead-Bone; it forms of the Scull. the upper Part of the Orbits of the Eyes, and Os Frontis. the Forehead; and joins the Bones of the Sinciput and Temples, by what is call'd the Coronal Suture. (2.) and (3.) The two Bones of the Sinciput, call'd Parietalia, which make the Sides of the Scull, Parietalia. and are join'd to one another in the Crown of the Head, by the Sutura Sagittalis. (4.) and (5.) The Offa Temporum, or two Bones of the Tem- Ola Tempoples; they are fituated in the lower Part of the Sides of the Scull, and are join'd to the Parietalia by the Sutura Squamofa. (6.) The Os Occipitis, Os Occipitis. or Bone of the Occiput or Hinder-part of the Head; it joins the Offa Parietalia, by the Sutura Lambdoidalis.

rum.

ral Bones.

THE lower Part of each temporal Bone, being The Proceffes thick and hard, is call'd Os Petrofum or Stony of the TempoBone; they have alfo each three Proceffes, viz. (1.) The Zygomatic, which runs forward and unites with the Procefs of the upper Jaw-Bone, making the Bridge call'd Zygoma, under the Ear. (2.) The Mamillary or Mastoide Procefs, fituated behind the Paffage of the Ear. (3.) The Styliform Process, which ftrikes down from the Bafis of the Scull like the End of a Quill.

THERE are two Bones common to the Scull Bone of the and Upper Jaw, viz. (1.) The Sphenoides; it is Scull and fituate juft in the Middle of the Bafis of the upper Jaw. Scull; on its lower Side it has five Apophyses; ÖsSphænoides. two call'd the Pterigoides, or Wing-like Pro

ceffes;

ceffes; two others make the lower and internal Part of the Orbit of the Eyes; and the fifth a very small one, receiv'd in a Cavity at the further End of the Vomer. On its Infide it has four Proceffes call'd Clinoides, which form a Cavity Os Ethmoides, in the Middle call'd Sella Turcica. (2.) The O or Cribriforme. Ethmoides; it is fituated in the Middle of the Bafis of the Forehead-Bone; in the Middle of it is a fmall thin Procefs call'd Crifta Galli, from its Likeness to the Comb of a Cock. This Bone has its Name from the Number of finall Holes in it, which make it refemble a Sieve. From its under Side there goes a thin Bone, which divides the Cavity of the Nofe into two Parts call'd Noftrils: The lower Edge of this Bone is grov'd with the Vomer. On each fide this Partition are Ofa Spongiofa. the Offa Spongiofa, or Spongy Bones; the two external Plates whereof make part of the Orbit at the greater Canthus or Corner of the Eye.

Os Unguis.

Bones of the THE Bones proper to the Upper-Faw are Upper-Jaw. eleven; five on each Side, and one in the MidOs Mali. dle: They are as follow. (1.) Os Mali, Zygoma, or Cheek-Bone; it makes the highest Part of the Cheek, and the external Part of the OrOs Maxillare. bit of the Eye. (2.) The Os Maxillare is that Part in which all the Teeth of the Upper-Jaw are fet; its upper Side makes the lower and internal Part of the Orbit. (3.) The Os Unguis; it is a little Bone in the great Angle of the Orbit; in it is the Hole in which the Lachryma! Bag lies. (4.) The Os Nafi, or Bone of the Nofe; to this the Cartilages which divide the Noftrils are faften'd. (5.) The Os Palati, or Palate Bone; it makes the Hinder-part of the Roof of the Mouth, and joins the Os Maxillare, which makes the Fore-part. (6.) The eleventh and last is call'd the Vomer, being like a Plough fhare as it were; it has a Grove on its upper Part, which

Os Nafi.

Os Palati.

Vomer.

receives

receives the Septum Nafi, or Partition of the Nofe; it is join'd above on the further End to the Os Sphenoides, and on its lower Part to the Bones of the Palate.

THE Lower-Jaw is made of one Bone; its Bone of the anterior angular Part makes the Chin. At each Lower-Jaw. Extremity it has two Proceffes; the first, which is broad, thin, and pointed, is call'd Corone; the other, which is lower and flattish, with a fort of Head, is call'd Condylus; by means whereof the Lower-Jaw-Bone is articulated into the Sinus of the Os Petrofum. Each End of the Bafis of this Bone is call'd the Angle of the Lower-Jaw.

THE Teeth are next to be confider'd; they are of the Teeth. the hardest, smootheft, and whiteft Bones of the Body. They are formed in the Cavities of the Jaws, and are of the following Sorts. (1.) The Incifivi, or Cutters, fo call'd because pretty broad Incifivi. and sharp; they ftand foremost in each Jaw, and in each Jaw four. (2.) The Canini, or Dog- Canini. Teeth; these are two in each Jaw, one on each Side of the Incifivi; they are thick, round, and pointed, and are contain'd above two Thirds in their Alveoli or Sockets. (3.) The Molares, or Molares. Grinders; they are generally ten in each Jaw, five on a Side. Their Extremities are broad and uneven, and are inferted in their Sockets with two, three, and fometimes four Roots. With these we grind, as it were, our Aliments, to a State fit for Digestion in the Stomach.

THE SPINE or Back-Bone is made up of a Of the Spine, Chain of fmall Bones, which reaches from the and Vertebra. Bafis of the Scull to the Seat of the Body. These fmall Bones are call'd Vertebra; of which there are reckon'd 7 in the Neck, 12 in the Back, 5 in the Loins, 6 in the Os Sacrum, and 4 in the Os Coccygis. In each Vertebra we distinguish two Parts, viz. the Body, and the Processes thereof.

The