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 201 ANATOMY. Part II. vered by the perforatus. It is compofed of four mufcles, Antithenar five Semi-Interosse(us Pollicis. which at firft feem to make but one mafs, and afterwards This is a frtiall, flat, flefliy mufcle, fituated oblique- terminate in four tendons. ly between the firft phalanx of the thumb, and firft bone The fleftiy portions of the firft and largeft, and alfo of the fecond, are fixed in the fuperior parts of the ulna of the metacarpus.. It is fixed by one end toward the bafis of the firft me- and interofleus ligament, down to their middle ; the flefliy tacarpal bone, near the firft bone of the fecond row of portion of the third is joined to the tendon of the ulnathe carpus. From thence it runs obliquely toward the ris internus, by a fort of common aponeurofis ; and that head of the firft phalanx of the thumb, and is inferted of the fourth is fixed along the ulna. fmall collateral in the lateral external part of that bone, or on that fide The four tendons have often feveral which is turned to the firft metacarpal bone. It crofies tendons, fometimes five in number,1 united to the tenover the femi-interofleus indicis, this mufcle lying to.ward dons of the neighbouring mufcle, as they pafs under the the back of the hand, and the antithenar toward the large annular ligament of the carpus; but the tendons themfelves are feparated from the others by thin fepta, palm. which form a kind of particular rings. Being thus ftrengthened,, they feparate; and running along the palm PERFORATUS vulgo SUBLIMIS. of the hand in diftimft: membranous vaginae, like thole of This is a mufcle of a confiderable volume, lying along the perforatus, by which they are covered, they enter the infide of the fore-arm, flelhy for the greateft part the ligamentary vaginae of the firft phalanges together near the articulation of the fore-arm with the os humeri, with the former; and having paffed through the fiflures and near the carpus, terminating in four diftinfl portions, thereof, and through the ligamentary vaginae of the fewhich become the fame number of long fmall tendons. cond phalanges, they are inferted in the flat inner fide of The name of fublimis has been given to it, becaufe it the third, near their bafis. lies almoft onf the furface of the fore-arm; and that of perforatus, from the flits found near the extremities of EXTENSOR DIGITORUM COMMUNIS. its tendons. It is commonly made up of four mufcles, clofely uni- This is a compound mufcle, very much refembling ted by their fleftiy portions. It is fixed above to the fu- the perforatus and penforans, lying on the outfide of the perior internal parts of the ulna and radius, a.nd to that fore-arm, between the ulnaris externus and radialis exof the interofleus ligament. A little below the middle ternus. of the fore-arm, 'this large flelhy body is divided into It is fixed above, by a tendinous extremity, to the pofour diftinit mufcles, which, on the loweft quarter of fterior and lower part of the efxternal or great condyle the fore-arm, end in four flat tendons of different fizes. of the os humeri, and, by a tendinous adhefion on each Thefe four tendons are inclofed in a common membra- fide, to the ulnaris and radialis externus. It has likenous or mucilaginous vagina, which likewife. furnilhes wife fometimes a fraall infertion in the radius. It is dieach tendon with a particular thin vagina. In this man- vided into four mufcles, like the perforates and perfoner they advance to the carpus, and pafs under the large .rans, and four long, flender, fmall tendons. annular tranfverfe ligament. Beyond this ligament, they Three of thefe tendons pafs through the common exfpread again in the palm of the hand, ftill retaining their ternal annular ligament of the carpus; and the fourth, particular vaginse, and run between the aponeurofis pal- which goes to the little finger, pafles through a particular maris and metacarpus, toward the fingers, feparating ring of the fame liganient. Afterwards thefe four tendons feparate as they go to more and more by degrees. Having reached 'the heads <)f the metacarpal bones, the fingers, and in their pafl’age communicate with each they pafs under the four arches or frsena formed by the other, by oblique tendinous feries, chiefly near the heads furcae of the aponeurofis palmaris,, and particular fepta of the metacarpal bones. of the great tranfverfe ligament of the palm of the hand; Each tendon having reached the bafis of the firft phaand then each tendon having got beyond the head of one lanx, is flightly inferted therein by fome lateral expanfions metacarpal bone, and beyond the bafis of the firft pha- fixed in each fide of the bafis. From thence it advances lanx, enters the ligamentary vagina on the flat or inner to the head of the fame phalanx, where it is divided infide of that phalanx, and is inferted in the flat fide of to two flat portions, which, at the articulation of the the fecond phalanx, near its bafis, the membranous va- firft phalanx with the fecond, leave fome diftance begina accompanying it to its jnlertion. tween them. About the head of the fecond phalanx, In palling along the infide of the firft phalanx, the they unite again, and are fixed in the convex fide of the tendon is divided by a long flit, which gives paffage to a third phalanx, near its bafis. tendon of the perforans; and from thence the names of thefe two mufcles are taken. EXTENSOR INDICIS PROPRIUS. is a fmall long mufcle, with a long flender tenPERFORANS vulgo PROFUNDUS. don,This lying a little obliquely on the lower and outer half This mufcle is very like the former, and is fituated of the fore-arm, between the ulna and fore-fipger. much in the fame manner; only it lies lower, and is co- It is fixed, by its flefliy body, a little higher than the Vol. I. No. 9. 3 3E loweft