Page:Encyclopædia Britannica, first edition - Volume I, A-B.pdf/250

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A N A T O M Y. Part II. it terminates in a thick tendon, which is inferted in the BICEPS. pofterior. and interior fide of the inner condyle of the tiThis mufcle is made up of two portions, ctie long, bia, by three fhort branches, the .firft or uppermoft of the other fhort, and they end in a common fendon. which goes a little toward the infide, the lecond more Both portions are flelhy and cordiderably thick, being fi- backward, and the third lower down. tuated on the back .and outude of the thigh, between the buttock and ham. P O P L I TE U S. The great portion is fixed above, by a firong tendon, This is a fmall mufcle, obliquely pyramidal, fituated in the pollerior and lower part of the tuberofity of the under ham. ifchium, under the infertion of the inferior gemellus, and It isthefixed by a ftrong narrow tendon, to the clofe behind that of the femhnervofus. From thence it outer edge of above, the inner condyle of the os fecnoris, and runs down toward the lower extremity of the thigh, to the neighbouring pofterior ligament of the joint. ■where it meets the other portion, and joins with it in From thence it runs obliquely downward under the inner forming a common tendon. condyle of jhe os femoris; it is a fla,t and pretty thick fleftiy The fmall portion is fixed, by flelhy fibres, to the body, increafing gradually in breadth, till it is fixed in the outfide of the linea afpera, below its middle, and to the fafciaT lata, where it ferms a feptum between the triceps back-fide of the head of the tibia, all the way to the and aflus externus. From thence the fibres run down oblique line or imprpflion obfervable on that fide. a little way, and then meeting the great portion, a com- mon tendon is formed between them. Uses of the Mufclet ’which move the Boner of the Leg This ftrong tendon runs down to the outer and backOs Femoris. part of the knee, and is inferred in the lateral ligament The two vafti andon the ought to be looked upon of the joint, and in the head of the fibula, by two very as a true triceps, the crureus ufes of which, in relation to the ihort tendinous branches. bones, are only to extend the tibia on the os fenloris, and the os femoris on the tibia. The extenfion of the S E M I-N E R V O S U S. tibia on the os femoris happens chiefly when we fit or lie, that of the os femoris on the tibia when we ftand This is a longmufcle, half fielhy and half tendinous, and or walk. AH the three mufcles move the patella unior like a-nerve, from whence it has its name. It is fitu- formly in the direftion of the os femoris, on the pulley ated a little obliquely, on the pofterior and inner part of at the lower extremity of- that bone. the thigh. infertion of both the vafti immediately in the head It is fixed above to the pofterior part of the tuberofity of The the tibia, prevents the patella from being luxated laof the ifchium, immediately before, and a little -more in- terally on fome occafions, in which the mufcles may adt ward than the biceps. It is afterwards fixed, by flefliy more force on one fide than on the other, or refibres, to the tendon of the biceps, for about the breadth with main without adtion, in which cafe tire patella is loofe of three fingers, much in the fame manner as the cpraco- and floating. brachialis is fixed to the biceps of the arm. anterior, by its infertion in the patella, is a From thence it runs down flefhy toward the lower part The redlus to the haft three mufcles, and ferves to exteqd of the infide of the thigh, having a fort of tendinous in- congener leg. By its infertion in the os ilium, it bends the terfedlion in the inner part of its flefliy portion. Having the and aflifts the pfoas, iliacus, and paftineus, whereached below the middle of the thigh, it terminates in thigh, the leg be extended or bent. It likewife moves the a fmall, long, round tendon, which runs down to the ther pelvis forward on the os femoris, and hinders it from infide of the knee, behind that of the gracilis, where it falling back when we fit. expands in breadth. . It is inferted in the infide of the upper part of the ti- The fartorius performs the rotation of the thigh bia, about,two or three fingers breadth below the tube- from before outward, whether extended or bent; beiqg rofity or fpine, immediately under the tendon cf the gra- an antagonift to the mufculus fafcke latse, and a congener to the quadrigemini. cilis internus, with which it communicates. It likewife bends the thigh, or rajfes it forward ; it moves the pelvis forward on the femoris ; and when the S E M I-M E M B R A N O S U S. pelvis refts on the two tuberofities of the ifchium in fitThis is a long thin mufcle, partly tendinous, from ting, it keeps it in that fituation. whence it has its name, and fituated on the back-fide of Laftly, it bends the leg, whether it performs the rotation of the thigh at the fame time or not. the thigh, a little towards the infide. It is fixed above, by a broad tendon or long aponeu- The gracilis internus bends the leg much in the fame rofis, in the irregular, obtufe, prominent line whifih goes manner with the fartorius, which it aflifts in this funcfrom the acetabulum to the tuberofity of the ifchium, a tion, but not in that of turning the leg. little above the infertion of the femi-nervofus, and be- It may likewife aflift the triceps in die addudtion of the tween thofe of the gemellus inferior and quadratus. thigh, which it performs with much more facility than it From thence it runs down flefhy in an oblique diregion begins the flexion of the leg without the rotation of thebehind the inner condyle of the os femoris, below which thigh. The