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i6S A N A T O M Y. Part I. conne<£i this vettebra to the os occlpitis, and to the fe- tranfverfely from one rough protuberance of the firft vercond vertebra, are fixed. The back-part of the arch tebra to the other, and is cartilaginous in the middle, to is conCave, fmooth, and covered with a cartilage, in a move on it. recent fubjeft, to receive the tooth-like procefs of the The fijperior^oblique proceffes of this vertebra denfscond vertebra. In a firft vertebra, from which the tata are large, circular, very nearly in an horizontal pofecon'd has been feparated, this hollow makes the paf- fition, and fiightly convex, to be adapted to the inferior lage for the fpinal marrow to feem much larger than it oblique proceffes of the firft. vertebra. really is : On each fide of it a fmall rough finuofrty may The tranfverfe proceffes of the vertebra dentata are fee remarked, where the ligaments going to the fides of fhort, vjjy little hollowed at their upper part, and not th.e rooth-like procefs of the following vertebra are fatt- forked at their ends; and the canals through which the ened ; and on each fide, a fmall rough protuberance and cervical arteries pafs, are refle&ed outwards about the depreffion is obf'errable,. where the tranfverfe ligament, middle fubftance of each proceft; fo that the courfe of which fecurcs the tooth-like procefs in the finuofity, is thefe veffels may he direfted towards the tranfvede profixed, and hinders that procefs from injuring the medul- ceffes of the firft: vertebra. la fpinalis in the fleftions of the head. The fpinal procefs of this vertebra tendata is thick, The atlas has as little fpinal procefs as body ; but in- ftrong, and ftiort, to give fufficient origin to the mufeuli ftead thereof, there is a large bony arch, that the muf- redti majores, and obliqui inferiores, and to prevent the clcs which pafs over this vertebra at that place might contufion of thefe and other mufcles, in pulling the head not be hurt in extending the head. back. The fuperior oblique procelfes of this atlas are large, The third vertebra of the neck is by fome called axis; oblong, hollow, and more horizontal than in any other but this name is applied to it with much lefs reafon than vertebra. ^They rife more in their external than in- to the fecond. This third, and the three below, have ternal brim; by which their articulations with the con- nothing particular in their ftrintture; but all their parts dyloid of the os occipitis are firmer; Under the ex- come under the general defeription formerly given, each ternal edge of each of thefe oblique proceffes, is the fofi- of them being larger as they defeend. fa, or deep open channel, in which the vetebral arte- The fever.th vertebra of the neck is near to the form ries make the circular turn, as they are about to enter of thofe of the back, having the upper and lower furfaces the great foremen of the occipital bone, and where the of its body lefs hollow than the others:—The oblique tenth pair-of nerves goes out. ^-The inferior oblique proceffes are more perpendicular;—neither fpinal nor precedes extending from within outwards and down- tranfverfe proceffes are forked.—This feventh and the wards, are large, concave, and circular. So that this fixth vertebra of the neck have the hole in each of their vertebra, contrary to the other fix, receives the bones ,tranfverfe proceffes, more frequently divided by a fmall with which it is articulated both above and below. crofs bridge, that goes between the cervical vein and arThe tranfverfe proceffes here are not much hollowed tery, than any of the other vertebras. or forked, but are longer and larger than thofe of any The twelve dorfal may be diftinguilhed from the, other other vertebra of the neck, for the origin a^d infertion vertebras of the fpine by the following marks. of feveral mufcles. Their bodies are of a middle fize, betwixt thofe of The hole for the fpinal marrow is larger in this than the neck and loins;—they are more convex before than in any other vertebra, not only on account of the mar- either of the other two forts; and are flatted laterally row being largett here, but alfo to prevent its being hurt by the preffure of the ribs, which are inferted into fmall cavities formed in their fides. This flatting on their fides, by the motions of this vertebra on the fecond one. This large hole, and the long traverfe proceffes, make which makes the figure of thefe vertebrae almoil an half oval, is of good ufe; as it affords a firm articulation to this the broadeft vertebra of the neck. The condyles of the os occipitis move forwards and the ribs, allows the trachea arteria to divide at a fmail backwards in the fuperior oblique proceffes of this verte- angle, and the other large veffels to run fecure from the bra; but from the figure of the bones forming thefe a<ftion of the vital organs. Thefe bodies are more joints, it appears, that very little motion can here be al- concave behind than any of the other two claffes. lowed to either fide ; and there mutt be ttill lefs circular Their upper and lower furfaces are horizontal. The cartilages interpofed between the bodies of thefe motion. The fecond vertebra colli is called dentata, from the vertebrse'are thinner than in any other of the true vertebras ; and contribute to the concavity of the ffpine in the tooth-like procefs on the upper part of its body. The body of this vertebra is fomewhat pyramidical, thorax, by .being thinneft at their fore-part. being large, and produced downwards, efpeciaily at its The oblique proceffes are placed almott perpendicular; fore-fide, to enter into a hollow of the vertebra below ; the upper ones flaming but a little forwards, and the lowwhile the upper part has a fquare procefs with a fmall er ones flanting as much backwards.—They have not as point ftanding out from it. This it is that is imagined much convexity or concavity as is worth remarking. to refemble a tooth, and has given name to the verte- Between the oblique proceffes of oppofite fides, feveral bra.—The fide of this procefs, on which the hollow of ftrarp proceffes ftand out from the upper and lower parts the anterior arch of the firtt ‘vertebra plays, is convex, of the plates which join to form the fpinal procefs ; into fhiooth, and covered with a cartilage; and it is of the thefe (harp proceffes ftrong ligaments are fixed, for coniaroe form behind, for the ligament, which is extended nefting the vertebras. The
