Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/166

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tains the anterior lobes of the brain, and a portion of the lon- gitudinal finus, and forms the forehead, the upper parts of the orbits, and a portion of the temples. fFinfoivs anatomy, p. 21.

Cartilages of the Os humeri. The cartilage by which the hemif- phere of the head of the os humeri is covered, is gradually thicker toward the middle, and thinner toward the ed^es. The four furfaces of the tuberofities, which appear cartilagi- nous in dry bones, ferve only for the infertion of the ten- dons of four mufcles, which move the os humeri on the fcapula. The channel, or finus, between the two tuberofities is partly covered by a thin cruft, which appears rather ligamentary than cartilaginous, and partly by a tendinous ftratum. Thetro chlea and fmall head of the lower extremity of the os hmneri. are covered with a common cartilage, in which the fame- proportion of tbicknefs is obfervable, as in that of the up per extremities; and this holds indeed pretty generally of the convex articular cartilages : and the foflulx near the pul ley and fmall head, are covered with a thin cartilaginous and ligamentary varniih.

Ligaments of the Os burner:. The capfular,or mucilaginous lig; ment, loofely furrounds the whole articulation of the fcapula with the head of the os humeri. The true ligament of this joint feems to be made up of two forts of ligaments clofely united together, viz. of a capfular ligament, which furrounds the whole articulation, and of feveral true ligaments which run over, and clofely adhere to the former at different di- ftances. On the body of the cs bumei i there are two par- ticular ligaments, which may be termed the intermufcular, or Iatcral^ones : they are long, flat, thin, but ftrong and nar- row, fixed by one edge along the two lower thirds of th< bone, and reaching to both condyles; they are broad, pretty tight, and are very narrow at the upper part, but broader toward the condyles.

The lower extremity of the os humeri is joined to the hones of the fore arm, by two fafciculi of ligamentary fibres, one fixed to the internal condyle, the other to the external. Each fafciculus is compofed of fibres clofely joined together near the condyle, but afterwards parting in diftinct bands like goofe's foot. The capfular ligament is fixed to the condyles, and then covers them, and is afterwards fixed round both fides of this lower extremity above the foffulre. The fofTulse are flightly varuifhed over alfo with a cartilaginous fubftanci This capfula feems to be ftrengthened by a ligamentary wall, the fibres whereof crofs one another in different directions, and appears larger and loofer when the mufcles are feparated from it, than when clofely united to them in its natural ftate. Winslo-ufs Anatomy, p. 130,.

Os humeri fraclured. Fractures of the os humeri are leaf!; dan- gerous when near its middle, and much worfe when near its upper or lower head, k fometimes happens, that the frac- tured ends of this bone keep their places, but much more frequently they are found (lipped one over another; by which means the fractured limb is made fhorter than the found one : fometimes alfo, tho' much more rarely, it happens, that the divided ends of the bone recede from one another, by reafon of the weight of the arm, and by that means the fractured limb becomes longer than the found one. In fractures of this bone, where the ends of the divided bone have fliped one over another, as is ufually the cafe, there is required both force and /kill to reduce them, efpecially if the patient has tenfe nerves and larger mufcles, as is ufually the cafe in ftrono- men. To extend the arm on this occafion, the patient muft be feated on a high (tool, and an affiftant muft lay hold of Iiis arm firmly above the fracture, keeping his elbow gently bent; then the lower part of the arm beneath the fracture, is in like manner to be taken hold of, and the. arm is to be gently extended forward, by endeavouring to remove eafily each part from the other, in a right line. The furgeon is then to take hold of the fractured part of the arm, and with both his hands reduce the fractured bones into their proper places, while the arm is kept in a proper ftate of extenfion by the affiftants; and when they are replaced, the limb is to be rolled up with the proper bandages. Heifter's Surg. p. 127.

Os hyoides. Mr. Du Vernoy obferves, that the right fide of the os hyoides is fhorter than the left. Comment. Acad. Pe- trop. Tom. 7.

Cartilages of the Ossa innominata. Thefe are not fo numerous a: might be imagined, on examining the bones in a dried fkele ton, where we are apt to think we fee the dried remains of cartilages on the crifta of the os ilium, on the tuberofity of the os ifchium, and on the grooves and notches which give paf- fage to the tendons of mufcles; but none of thefe incruftations are true cartilages, but for the moft part tendinous, aponeu- rotic or ligamentary, which fubffances being dryed, look mOre like cartilages than the true cartilages themfelves in the fame ftate. The true cartilages of thefe bones in adults are properly five in number, three of which are common, and two proper. The find and principal common cartilage, is that which makes the fymphyfis of the ofTa pubis. This forms a kind of arch, which is more confiderable in men than in women i the two others join the offa ilium to the os fa-

ctum, but are thinner than that of the ofTa pubis. Trie pro- per cartilages are thofe which line the cotyloide cavities, irl the edge of each of which there is a notch or opening betweeri the anterior or inferior parts, and in the cavity itfelf there is a broad and fhallow depreifion, reaching from the notch be- yond the middle part of the cavity; all the reft of the ace- tabulum is covered with a very white, lbining, fmooth carti- lage, which terminates precifely at the edge of the cavity. IVinfew's Anatomy, p. 122. See Ilium. Ligaments of the Ossa inmminata. Thefe are of two kinds, com- mon and proper: the conynon ligaments arethofe which go between thefe and the neigbouring bones, of which there are a confiderable. number : One fuperior, inferted by one end m the internal labium of the pofterior part of the os ilium; one inferior and anterior, fixed by one end in the inner fide of the crifta of the os ilium, and by the other in the fuperior and anterior part of the firft falfe tranfverfe apophyfis of the os facrum. Several inferior and pofteri or, fixed by one end along; the internal labium of the tuberofity of the crifia of the os ilium, and by the other in the firft three falfe tranfverfe apo- phyfes : and to this muft be added the ligaments by which the os femoris is joined to the os irmominatum. The principal pro- per ligaments are four : the two facro-fciatic, the obturator, and the inguinal, which fee under their proper heads; but befide thefe, there is another fmall, flat, and very fironc li- gament, which runs tranfverfely between the two angles of the cotyloide notch, and may be termed the proper, or tranf- verfe ligament thereof. The elaftic border-of the cotyloide cavity may llkewife be reckoned among the ligaments: it is a fort of additional piece, ftrongly united to the edge of the cavity, but eafily yielding any way, on preflure. The two ligaments by which the os femoris is connected to the os innomi- natum, are alfo inferted in this bone; one of thefe lio-aments furrounds the whole articulation, and the other is contained in it : the firft is called the orbicular ligaments, the other, tho* very improperly, the round ligament: the orbicular is very ftrong, and unequally thick, and furrounds the whole convex circumference of the fupercilium of the cotyloide cavity. The ligament which lies in the joint is not round, but is a flat cord, broad at one end, and narrow at the other, and is in fome degree of a triangularfhape. Winfl^i Anatomy, p. 122. Os innominaimn fraclured. A fracture of this, bone very feldom happens; but when it does, it is readily difcovered by the in- jury and fymptoms in the neighbouring parts, and is the more particularly dangerous, when the patient difcharges a brown bloody matter. In reftoring this bone, the patient muft lie down on his found fide; the bone muft be replaced with the hands, covered with comprefTes, dipt in fpirit of wine, and kept^ on by the fpica bandages. , Afterwards bleeding, with cooling and relaxing medicines, muft be ufed, and a thin diet obferved. Heifter's Surg, p. 126. Os orbiculare. This, in the carpus, is the fourth bone of the firft row. It has its name from the roundnefs of its figure, and is, for the fame reafon, by fome called os pijifonne, and os lenticulare; it is, however, not perfectly, or regularly round; it has but o$e cartilaginous fide, which is irregularly orbicular, and the border, a circumference of which repre- fents a kind of narrow collar. The reft of the bone is rough, convex, and irregularly round, making one of the four emi- nences, on the concave fide of the carpus. This bone, and the os cuneiforme, may be fuppofed to make a third row, dif- ftinct from the other two. JFinflow's Anatomy, p. 83. Nafi Ossa. See Nasi offa. Palati Ossa. See Pal a ti offa. Pcr'ietalia Ossa. SeePARiETALiA offa. PeftorisOssA. See Pectoris offa.

Os facrum (Cyd.) — As this bone is the bafis by which the whole fpine is fupported, it has by fome been called os ba/i/are; its figure comes near that of a long triangle, with the bafis upward, and apex downward. Anatomifts, in its defcription, divide it into the upper part, or bafis, the lower, as it is fituated, or apex; two fides, the anterior, or concave, and the pofterior, or convex; and two lateral parts, or edges. The pieces of which it is compofed in infants, called falfe vertebra, are five in number, and are united together by cartilages, which in time almoft difappear, leaving only lit- tle ridges, or lines, more or lefs prominent in their places. The firft of thefe is much larger than any of the true ver- tebra?, but their fize diminifhes by very great degrees as they defcend; fo that the loweft which makes the point of the os facrum, has fcarcely the appearance of a vertebra. At the ba- fis, or upper purt, of the os facrum, are two articular apophy- fes, anfwering to the inferior ones of the laft vertebra of the loins. Below each of thefe apophyfes laterally is a large notch, and between them, we fee diftinctly enough the body of this firft falfe vertebra, which, is like that of the lumbar ver- tebra?, being very much inclined backward; fo that the body of this firft falfe vertebra, as well as that of the laft true one, is longer before than behind; and from this obliquity it is that the os facrum and laft lumbar vertebra, form at their connec- tion, a very confiderable angle. The lateral parts- are broad at top, forming on each hand a large, irregular, cartilaginous furface, in the figure of a great S, and fometimes of a'bird's

head.