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 2oo ANA! ■ O M Y. Part II. it terminates in two long flat tendons, more or With the uinaris externus it inverts the hand, turn- vsded, fubdivided, which pals together under a particular ing the convex fide of the metacarpus toward the lower lefs extremity of the bones of the fore-arm. It likewife annular ligament, being only parted by fepta or frsena'belonging to that ligament. moves the fecond row of the carpus on the firfh This mutcle, aSing alone, draws obliquely, and to- The firft of thefe two principal tendons is inferted in ward the external angle of the radius, that portion of the edge of the bafis of theErft phalanx, near the large, tranfverfe ligament of the carpus. When this tendon is the hand which anfwers to the firft metacarpal bone, and fubdivided, the other portion of'it is fixed in that bone to the index. the carpus which fuftains the thumb. The other The ulnaris gracilis, commonly called palmaris longus, ofprincipal which often belongs to a mufcle entirefeems to be an affiitant to the ulnaris and tadialis interni ly diftinAtendon, the former, is fixed in the convex fide of in bending the wrid; and it feems likewife particularly the bafis. offrom the fecond phalanx, where it joins the tento affift the radialis internus in the motion of pronation. don of the extenfor fecundus. The metacarpius ferves to turn the fourth bone of the fecundus is ftxorter than the firft. It is metacarpus toward the thumb, and at the fame time to fixedThetoextenfor below the former, and above the inincreafe the convexity of the back of the hand, which is fertion ofthetheulna,extenfor proprius, and likewife to called making Diegener's cup. The fourth bone thus the neighbouring part ofindicis the interofleous ligament. From moved carries the third along with it by reafon of their thence it runs down obliquely on the middle part of the connexion, which ftill augments the hollow on one fide, radius, where it has likewife a fmall adhefion. Afterand the convexity on the other. wards it palfes through the fmall channel in the ftyloid apophyfis of the radius, through the annular ligament to the tendons of the radialis externus, and Sect. VIII. The Muscles which move the belonging over thefe tendons, being parted from them by a fmall liFinpcrs. gamentary feptum. It is inferted in the convex patt of the third phalanx, near its bafis. FLEXOR POLLICIS LONGUS. THENAR. This is a long mufcle, fixed by'fliort and oblique flefny fibres to the infide of the upper part of the inter- This is a very thick flefhy mufcle, in fome meafure offeous ligament, near the radius, and along that bone pyriform, lying on the firft phalanx of the thumb toall the way down to the pronator quadratus. There it ward the palm of the hand, the large eminence in which terminates in a flat tendon. by it. This tendon having paffed under a particular ligament, is chiefly formed to the bone which fupports the thumb,, and runs in between the two portions of the thenar, and then to Ittheis fixed neighbouring great internal annular into a fort of groove left between the two fefamoide ligament of the carpus.part Itofis the meafure bicipita!], bones fixed to the bafis of the fecond phalanx of the two diftinft portions anfweringintofome the two infertions althumb, on that fide which is turned to the palm of the ready mentioned. As it runs along the firft phalanx, hand. Afterwards the tendon ends in the flat fide of thefe two portions unite, and, dimialfliing in thicknefs, the third phalanx, near its bafis. It is inclofed in a li- are both inferted by one tendon in the lateral gamentary vagina, from the annular ligament to its in- part of the head of the firft phalanx, in the lateralinternal iertion, and it is divided or flit, fo that it appears to be of the bafis of the fecond, and in the lateral ligamentpattof inferted by two extremities adhering together by their ihat joint. edges. MESOTHENAR. EXTENSORES POLLICIS. This is a flat, and nearly triangular mufcle, lying beThese are two very dilKnft mufcles, the firft or long- tween firft phalanx of the thumb, -and the bottom eft of which is fometimes more, fometimes lefs, and of the the of the hand. fometimes altogether divided into two, in which cafe It is palm inferted, by a very broad bafis, in the ligament thefe mufcles are three in number. They are fituated which connects the os magnum of the carpus to that obliquely between the ulna and convex fide of the thumb. which fupports the thumb. is likewife inferted along The extenfor primus is a long mufcle, more or lefs the internal or angular pa*t ofIt that bone of the metacardouble, in the manner already faid. It is fixed above by pus, which fupports the middle finger, and in the fmall flefliy fibres, firft to the outfide of the ulna, near its up- extremity of that which anfwers to the index. per extremity, below the anconaeus minor and infertion From thence the fibres contradting to an angle, termiof the ulnaris externus ; next, to the interofleous ligament nate in a flat tendon of different breadths, which is inunder the fupinator brevis; and, laftly, to the middle ferted in that fide of the head of the firft phalanx of the part of the outfide of the radius. which is turned to the hollow of the hand, and From thence it runs down and paffes anteriorly over inthumb the neighbouring part of the bafis o^ the fecond phathe lower part of the radius, and tendons of the fupina- lanx, by tor longus and radialis externus, and being gradually di- that joint.means of the fecond fefmioid bone belonging Antithenar