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 171 Part I. ANA' r O M Y. allowing confiderable motion to this laft bone, was it not the leaft mark of their former reparation remains : notmuch confined by ligaments. Laterally, the os facrum withftanding, they are deferibed as confifting each of bones, to wit, the os ilium, ifehium, and pubis. is joined to the ofl'a ilium by an immoveable fynchon- three Os Ilium, or haunch-bone, is fituated higheft of the drofis. and reaches as far down as one third of the great The ufes of the os facrum are, to ferve as the com- three, which the head of the thigh-bone is received. mon bafe and fupport of the trunk of the body, to guard cavity into external fide of this bone is unequally convex, the nerves proceeding from the end of the Ipinal mar- andThe called its dorfum;—the internal concave furface row, to defend the back-part of the pelvis, and to af- is byisfome (but improperly) named cojla. The femiford fufficient origin to the mufcles which move the trunk circular edge at the higheft part of this bone, which is and thigh. wdth a cartilage in the recent fiubjedt, is named Os Coccygis, or rump-bone, is that triangular tipped chain of bones depending from the os facrum; each bone the fpine, into which the external or defeending oblique of the abdomen is inferted; and from it the inbecoming fmaller as they defcend, till the laft ends almoft mulcjeafeending oblique and the tranfverfe mufcles of the in a point. The os coccygis is convex behind, and con- ternal cave before ; from which crooked pyramidal figure, belly, with the glutreus maximus, quadratus lumborum, which was thought to referable a cuckow’s beak, it has. and latiffimus dorfi,.have their origin.—The ends of the fpine are more prominent than the furface of the bone begot its name. This bone confifts of four pieces in people of middle low them; therefore are reckoned procefles. From age:—In children, very near the whole of it is carti- the anterior fpinal procefs, the fartorius and fafcialis lage : In old fubjefts, all the bones are united, and mufcles have their rife, and the outer end of the doubled become frequently one continued bone with the os fa- tendon of the external oblique mufcle of the abdomen, commonly called Fallopius'% or Poupart's ligament, is crum. The higheft of the four bones is the largeft, with fixed to it. The infide of the pofterior fpinal pro/boulders extended farther to each fide than the end of cefs, and of part of the fpine forward from that, is made the os facrum;—the upper furface of this bone is a little flat and rough where the facro-lumbalis and lopgiffimus hollow. From the back of that bulbous part called its dorfi rife ; and to its outfide ligaments, extended to the Jboulders, a procefs often rifes up on each fide, to join os facrum and tranfverfe proceffes of the fifth and fourth, with the bifurcated fpine of the fourth and fifth bones vertebras of the loins, are fixed. Below the anterior of the os facrum, to form the bony bridge mentioned in fpinal procefs another protuberance Hands out, which, the defcription of the os facrum. Immediately below by its lituation, may be diftinguilhed from the former, the fhoulders of the os coccygis, a notch may be remark- by adding the epithet of inferior, where the mufculus. ed in each fide, where the thirtieth pair of the fpinal redlus tibke has its origin.—Betwixt thefe turn anterior nerves paffes. The lower end of this bone is form- procefles the bone is hollowed where the beginning of ed into a fmall head, which very often is hollow in the the fartorius mufcle is lodged. Below the poftefior fpinal procefles, a fecond protuberance of the edge of middle. The three lower bones gradually become fmaller, and this bone is in like manner obfervable, wdiich is clofely are fpongy; but are ftrengthened by a ftrong ligament applied to the os facrum. Under this laft procels a which covers and connects them. Their ends, by confiderable large niche is obfervable in the os ilium ; which they are articulated, are formed in the fame man- between the fides of which and the ftrong ligament that ner as thofe of the firft bone are. is ftretched oyer from the os facrum to the ftiarp-pointed The lower end of the fourth bone terminates in a procefs of the os ifehium of the recent fubjeft, a large hole is formed, through which the mufculus pyriformis, rough point, to which a cartilage is appended. To the fides of thefe bones of the os coccygis, the the great fciatic nerve, and the pofterior crural veflels, coccygaei mufcles, and part of the levatores ani, and of pals, and are prote&ed from comprelfion. the glutaei maximi, are fixed. The external broad fide, or dorfum of the os ilium, is The os coccygis ferves to fuftain the inteftinum rec- a little hollow towards the fore part; farther back it is as tum ; and, in order to perform this office more effectu- much raifed; then is confiderably concave ; and, laltly, it is ally, it is made to turn with a curve forwards; by which convex. Thele inequalities are occafioned by the actions alfo the bone itfelf, as well as the mufcles and tegu- of the mufcles that are fituated on this furface.—From ments, is preferved from any injury, when we fit with behind the upperraoft of the two anterior fpinal procefles,. in fuch bones as are ftrongly marked by the mufcles, a our body reclined back. The fecond part of the trunk of the fkeleton, the femicircular ridge is extended to the hollow paflage of Pelvis, is the cylindrical cavity at the lower part of the fciatic nerve. Between the fpine and this ridge, the the abdomen, formed by the os facrum, os coccygis, glutsEUS medius takes its rife. Immediately from above and offa innominata ; which laft therefore fall now in the loweft of the anterior fpinal procefles, a fecond ridge cotirfe to be examined. is ftretched to the niche. Between this and the former The Ossa Innominata are two large broad bones, ridge, the glutasus minimus has its origin.^ On the which form the fore-part and fides. of the pelvis, and the outlide of the pofterior fpinal procefles, the dorfum of lower part of the fides of the abdomen.—In children the os ilium is flat and rough, where part of the mufcueach of thefe bones is evidently divided into three; lus gluteus maximns and pyriformis rifes.——-The lowwhich are afterwards fo intimately united, that fcarce eft. part of this bone is the thickeft, and is formed into a.