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 175 Part I. A N A T O M Y. is turned to one fide, or obliquely forwards or backThe Sternum, or breaft-bone, is the broad flat bone point wards.—Frequently it is all nearly of an equal breadth, or pile of bones, at the fore-part of the thorax.—In and fubjeds it is bifurcated; whence Come wriadults of a middle age, it is compofed of three bones, ters ingivefeveral the name of furcella, or furcula inferior-, which eafily feparate after the cartilages conne&ing them or elfe it isit unoflified the middle. In the greateft are deftroyed. Frequently the two lower bones are number of adults it is inoflified, tipped with a cartifound intimately united; and very often in old people, lage ; in fome, one half of it is and cartilaginous; and in othe fternum is a continued bony fubftance from one end thers, it is all in a cartilaginous ftate.—Generally feveral to the other; though we ftill obferve two, fometimes oblique ligaments, fixed at one end to the cartilages three, tranfverfe lines on its furface; which are marks of the ribs, and by the other to the outer furface of the xi-of the former divisions. When we coufider the fternum as one bone, we find it phoid-bone, conned it firmly to thofe cartilages. The ufes of the fternum are, to afford origin and inbroadelt and thickeft above, and becoming fmaller as it fertion mufcles; to fuftain the mediaftinnm, defcends. The internal furface of this bone is fomewhat to defendtothefeveral organs, the heart and lungs, at the hollowed for enlarging the thorax; but the convexity on fore-part; and,vitallaftly, by ferving as a moveable fulcrum the external furface is not fo confpicuous, becaufe the fides are preffecL outwards by the true ribs ; the round of the ribs, to aifift confiderably in refpiration. heads of whofe cartilages are received into feven fmooth pits, formed in each fide of the fternum, and are kept firm there by ftrong ligaments, which, on the external OF THE SUPERIOR EXTREMITIES. fuperior extremity is divided into the Jhoulder, furface, have a particular radiated texture.—The pits at, arm,Each fore-arm, and hand. the upper part of the fternum are at the greateft d:ftance Shoulder confifts of the clavicle and fcapulci one from another, and, as they defeend, are nearer; fo The Clavicula, or collar-bone, is the long crooked bone, that the two lowed are contiguous. like an Italic /, placed almoft horizontally The firft of the three bones that compofe the fternum, in figure like the upper lateral part of the fternum, and what all agree, is fomewhat of the figure of a heart, as it is isbetween commonly called the top of the ftioulder, which, as a commonly painted ; only it does not terminate in a fharp ckvis r beam, it bears off from the trunk of the body. pcin. This is the uppermoft thickeft part of the Theorclavicle, as well as other long round bones, is lienutm. The upper middle part of this firft bone, where it is larger at its two ends than in the middle. The end next to the fternum is triangular: The angle behind is confithickeft, is hollowed, to make place for the trachea ar- derably produced, to form a ftiarp ridge, to which thS teria; though this cavity is principally formed by the ligament extended from one 'clavicle to the obone being raifed on each fide of it, partly by the cla- tranfverfe ther is fixed.—The fide oppofite to this is fomewhat vicles thrufting it inwards, and partly by-the fterno-ma- rounded.—The middle of this protuberant end is as irftoidei mufcles pulling it upwards. On the cutfide of each tubercle, there is an oblong cavity, that, in view- regularly hollowed, as the cavity in the fternum for reing it tranfverfely from before backwards, appears a little ceiving it is raifed; but, in a recent fubjeff, the irreguconvex: Into thefc glente the ends of the clavicles are re- lar concavities of both are fupplied by a moveable carticeived.—In the fide of the under end of this firft bone, lage, which is not only- much more elofely conneded the half of the pit for the fecond rib on each fide is every where, by ligaments, to the circumference of the formed. The upper part of the furface behind is co- articulation, than thofe of the lower jaw are; but it vered with a ftrong ligament, which fecures the cla- grows to the two bones at both its internal and externrd ends ; its fubftance at the internal end being foft, but vicles. The fecond or middle divifion of this bone, is much very ftrong, and refembling the intervertebral cartilages. longer, narrower, and thinner than the fiift; but, ex- From this internal end the clavicle, for about two fifths cepting that it is a little narrower above than below, of its length, is bended obliquely forwards and downit is nearly equal all over in its dimenfions of breadth wards. On the upper and fore-part of this curvature a or thicknefs. In the fides of it are complete pits for fmall ridge is feen, with a plain rough furface before it; the third, fourth, fifth, and fixth ribs, and an half of whence the mufculus fterno-hyoideus and fterno-maftoideus have in part their origin.—Near the lower angle, a the pits for the fecond and feventh. Tire third bone is much lefs than the other two, and fmall plain furface is often to be remarked', where the firft: has only one half of the pit for the feventh rib formed rib and this-bone are contiguous, and are connedcd -by a in it; wherefore it might be reckoned only an appendix firm ligament. From this a rough plain furface is exof the fternum. In young fubjeds it is always carti- tended outwards, where the pedoral mufcle has part of laginous, and is better known by the name of cartilage its origin. Behind, the bone is made fiat and rough y'tpboides, or enfiforntis, than any other; though the an- by the infertion of the larger (hare of the fubclaviari cients often called the whole Jlernum e>:ftforme.—This mufcle. After the clavicle begins to be bended third bone is feldom of the fame figure, magnitude, or backwards, it is round, but foon after becomes broad and fituation in any two fubjeds; for fometimes it is a plain thin; whichfhape it retains to its external end. Atriangular bone, with one of the angles below, and per- long the external concavity, a rough finuofity runs, from pendicular to the middle of the upper fide, by which it which fome part of the deltoid mufcle takes its rife: U conneded to the fcccnd bone.—■—In other people, the ‘ -Gppofite to this, on the convex edge, a -fcabrous