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 Fai t T. 172 A N A T O M Y. large cavity with high bo-ima, to aflift in coropofing the the long head of the biceps flexor tibiae and feminervofus mufcles., and the femimembranofus riles from the extegreat acetabulum. The internal furface <3f the os ilium is concave in its rior one, which reaches higher and nearer the acetabubroadeft fore part, where the internal iliac mufcie has its lum than the other. The lower, thinner, more fcaorigin, and feme (hare of the inteftinum ilium and. colon brous part of the knob which bends forwards, is alfo is lodged. 'From this large hollow, a fmall Gnuofity is marked with two flat furfaces, whereof the internal is continued obliquely forwards, at the inGde of the anterior what we lean upon in fitting, and the external gives rife to inferior fpinal procefs, where part of the pfoas and iliacus the largeft head of the triceps addu&or femoris. Bemufcles, with the crural veffels and nerves, pafs.—■—- tween the external margin of the tuberofity, and the great The large concavity is bounded below by a (harp ridge, hole of the os innominatum, there is frequently an obtufe which runs from behind forwards, and, being continued ridge extended down from the acetabulum, which gives with fuch another ridge of the os pubis, forms a line of origin to the quadrants femoris.—As the tuber advances partition between the abdomen and pelvis. Into this forwards, it becomes fmaller, and is rough, for the oriridge the broad tendon of the pfoas parvus is inferted. gin of the mufculus traV'verfalis and eredtor penis. All the internal furface of the os ilium, 8ehind this The fmall leg of it, which mounts upwards to join the ridge, is very uheqnal : For the upper part is flat, but os pubis, is rough and prominent at its edge, where the fpongy, where the facro-lumbalis and longiffinftis dorG two lower heads of the triceps or quadriceps addudto^ rife.- Lower down, there is a tranfverfe ridge from femoris take their rife. which ligaments go out to the os facrum. Immedi- The upper and back part of the os ifehium is broad ately below this ridge, the rough unequal cavities and and thick; but its lower and fore-part is narrower and prominences are placed, which are exactly adapted to thinner. thofe deferibed on the Gde of the os facrum. In the The os ilium and pubis of the fame fide are the only fame manner, the upper part of this rough furface is po- bones which are contiguous to the os ifehium. rous, for the Grmer adhdiqn of the ligamentous cellular The Os Pubis, or jhare-hone, is the lead of the fuhftance ; while the lower part is more folid, and co- three parts of the os innominatum, and is placed at the vered with a thin cartilaginous (kin, for its immoveable upper fore-part of it.——-The thick larged part of this bone is employed in forming the acetabulum; from which, articulation with the os facrum. Os Ischium, or hip-bone, is of a middle bulk between ^becoming much fmaller, it is dretched inwards to its felthe two other parts of the os innominatum, is Gtuated low of the other fide, where again it grows larger, and lowed of the three, and is of a very irregular Ggure.— fends a fmall branch downwards to join the end of the fmall Its extent might be marked by an horizontal line drawn leg of the os ifehium.—>—The upper fore-part of each os near through the middle of the acetabulum; for the up- pubis is tubgrous and rough where the mufculus reftus pCr bulbous part of this bone forms fome lefs than the and pyramidalis are inferted. From this a ridge is exlower half of that great cavity, and the fmall leg of it tended along the upper edge of the bone, in a continued rifes to much the fame height on the other fide of the line with fuch another of the os ilium, which divides the abdomen and pelvis. The ligament of Fallopius is great hole common to this bone and the os pubis. the internal end of this ridge, and the fmooth From the upper thick part of the os ifehium, a (harp fixed tobelow it is made by the pfoas and iliacus internus procefs, called by fome fpinous, (lands out backwards, hollow mufcles palling with the anterior crural veflels and nerves from which chiefly the mufculus coccygaeus and fuperior behind the ligament. Some way below the former gemellus, and part of the levator ani, rife; and the an- ridgej another is extended from the tuberous part of the terior or internal facrofciatic ligament is fixed to it. Immediately below this procefs, a GnuoGty is formed for os pubis downwards, and oupwards towards the acetabuthe tendon of the mufculus obturator internus. In lum ; between thefe two ridges the bone is hollow and a recent fubjeid, this part of the bone, which ferves as fmooth, for lodging the head of the peftineus mufcie. a pully on which the obturator mufcie plays, is co- Immediately belovi', where the lower ridge is to take the vered with a ligamentous cartilage, that, by two or turn downwards, a winding nitch is made, which is comthree fmall ridges, points out the interllices of the prehended in the great foramen of a (keleton, but is fibres in the tendon of this mufcie. The outer fur- formed into a hole by a fubtended ligament in the reface of the bone at the root of this fpinous procefs is cent fubjeft, for the paflage of the poflerior crural nerve, made hollow by the pyriformis, or iliacus externus an artery, and a vein. The internal end of the os pubis is rough and unequal, for the firmer adhefion of mufcie. Below the GnuoGty for the obturator mufcie, is the the thick ligamentous cartilage that connefts it to its felgreat knob or tuberoGty, covered with cartilage or ten- low of the other fide:—The prweefs which goes down don. The upper part of the tuberofity gives rife to from that to the os ifehium is broad and rough before, the inferior gemellus mufcle. To a ridge at the infide where the gracilis and upper heads of the triceps, or raquadriceps adduftor femoris, have their origin. of this, the external or poflerior facrofciatic ligament is therBetwixt the os ifehium and pubis a very large irregufo fixed, that between it, the internal ligament, and the Gnuofvty of the os ifehium, a pafiage is left for the inter- lar'hole is left, which, from its refemblance jo a door nal obturator mufcie. The upper thick fmooth part or (hield, has been called thyroides. This hole is all, of the tuber, called by fome its dorfum, has two ob- except the nitch for the pofterior crural nerve, filled up, lique impreflions on it. The inner one gives origin to in a recent fubjeft, with a llrong ligamentous membrane, that