Page:Encyclopædia Britannica, first edition - Volume I, A-B.pdf/248

 O M Y. Part II. 20(5 A N A 1 ■from thence to the great trochanter of the os femoris, thigh from the other, when we (land, and that more or lefs diredlly according to the action of its anterior, pobehind the neck of that bone. portions. It is fixed by fleihy fibres to the outer anterior fide of fterior, orwemiddle fit, the only ufe of this mufcle is to perthe os pubis, all the way to the foramen ovale, to the formWhen the rotation of the os femoris about its axis, in edge of that hole, next the fmall ramus of the ifchium, and a little to the neighbouring parts of the obturator fuch a manner, that if the leg be bent at the fame time, it fhail be feparated from the other. ligament. From thence its fibres, contracting in breadth, pafs The glutaius minimus has likewife been reckoned an on the forefide of the great ramus of the ifchium, under extenfor of the thigh, but without any foundation. It affifts the glutseus medius in the abdu&ion of the thigh the acetabulum, where a tendon is formed, which con- when we ftand, and in the rotation when we fit. tinues its courfe behind the neck of the os femoris toward the great trochanter, and is inferred between the The pfoas bends the thigh on the pelvis, or brings it gemelli and quadratus, in a fmall foflula between the forward. It may likewife move the pelvis on the thighs, apex of the great trochanter, and the bafis of the col- and hinder it from being carried along with the reft of the trank, when the body is inclined backward while we lum femoris. fit, having the low'er extremities fixed by fome external force. In this fituation it may likewife move the verteQU A D R A T U S. bras of the loins. The iliacus is a congener or alfiftant to the pfoas, in This is a fmall, flat, flelhy mufcle, of the figure of bringing thigh forward and upward. It may likewife an oblong fquare, from whence it has it name. It is move thethepelvis manner with the former. fituated tranfverfely between the tuberofity of the ifchium The pe&ineusin istheanfame afliftant to- the two former mufand the great trochanter. cles in moving both the thigh and the pelvis. It may It is fixed, by one extremity along that obtufe line likewife in Bringing the thigh ijjward, or toward which runs from under the acetabulum, toward the lower other,afliftwhether it be extended or bent at the fame part of the tuberofity of the ifchium. From thence it the runs direftly toward the great trochanter, and is inferr- time. three triceps mufcles join in the fame ufe; that ed in almoft all the lower half of the oblong eminence in is, The move the thigh inward, and bring the two thighs that apophyfis; but chiefly in the fmall rifing or tubero- neartoeach other; as when, in riding, we prefs the thighs lity in the middle of that eminence. clofe againft the faddle; when, in fitting, we hold any thing clofe between the knees ; when we crofs the thighs; MUSCULUS FASCIiE LATJE. or when, in (landing, we bring the legs clofe together, in This is a fmall and pretty long mufcle, fituated a order to jump. little obliquely upward and downward on the forepart of The ufe of thefe mufcles is likewife to hinder the thighs from feparating more than is convenient, efpecialthe hip. It is fixed above to the outfide of the anterior fuperior ly in great efforts and jerks. fpine of the os ilium, between the infertions of the glu- The pyriformis, gemelli, and quadratus, called liketacus medius and fartorius. From thence its fleftiy fibres wife by the common name of quadrigemini, are congerun down a little obliquely backward, forming a very neres in their ufes ; and thefe have been confined by anafiat body, four fingers breadth in length, and two in tomifts to the rotation of the os femoris about its axis from before outward, when we ftand or lie at full breadth. This body lies between two laminse of the fafcia lata, length ; likewife in fitting, or when the thigh is bent in and is inferred therein by fliort tendinous fibres, which any other pofture, they carry the thigh outward, or fectiiappear at that place where the fafcia adheres to the parate the two thighs from each other when bent. great trochanter and tendon of the glutseus maximus. All the four co-operate in thefe two ufes of rotation and abduftion ; but they co-operate equally or unequally, according to the different degrees of the extenfion or Uses of the Mufchs 'which move the Os Femoris on flexion of the thigh. the Pelvis. obturator internus has nearly the fame ufes with The glutseus maximus ferves chiefly, by its pofterior theThequadrigemini, the rotation of the thigh portion, to extend the os femoris, and to draw it back- when extended, andin themaking when bent. ward. By its anterior portion, it may co-operate with The obturator externusabdfeHon concurs with the internus in the reft in performing the abdudtion of the thigh; but the fame ufes, though in a more Ample and in when we fit, it can do this office only by its pofterior a more uniform direftion. It ads chieflymanner, when the thigh portion. is extended more or lefs. By its infertion in the os coc'cygis, it may on fome mufculus fafcix latae makes a rotation from beoccafions bring it forward, and hinder it from being thruft foreTheinwards, that is, in a contrary diredion to that too far backward, as in the excretion of hardened feces, made by the quadrigemini and obturator internus ; and or in difficult births. this rotation is not lo much confined as that of the quaThe glutseus medius is commonly, but falfely, reckon- drigemini, becaufe it may have place whether die thigh ed an extenfor of the thigh. Its ufe is to feparate one be bent or extended. Sect.