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 Part II. ANA T O M Y. 205 all the three phalanges together ; and likewife each pha- againft each other, but do not feparate them all, nor lanx by itfelf, though not with the fame facility. move each finger in particular toward, or from, the The proper extenibrs of the fore and little fingers are thumb. In a general feparation of all the fingers, the aiTillants to two fubaltern mulcles of the extenfor com- interoflei move only the middle and ring fingers ; the inmunis that go to thefe fingers, which confequently we dex and little finger being feparated by other mufcles. extend feparately with more cafe than either of the o- In the motions of the fingers toward the thumb, which ther two. Thefe mufcles likewife ferve to bring the is termed udduttion, they ad only on three fingers, the fingers, in which they are inferted, near the other fin- middle, ring, and little fingers. In the contrary mogers. tion, or abdudion of the fingers, they move likewife The flexor pollicis longus ferves- chiefly to bend the three, viz. the index, middle, and ring fingers. third phalanx of the thumb, in which it is inferted by The ufes of the interoffei in particular, whether exthe extremity of its tendon. It likewife bends the fe- ternal or internal, may be different in different fubjeds, cond phalanx, by virtue of the ligaraentary vagina, according to the variety of their infertions ; and therethrough which it paffes, as through an annular ligament. fore in living bodies nothing can be determined about The firfl extenfor of the thumb alone, when there are them. three, a portion of the firft, when there are but two, According to the fituation in which they have been deferves to draw the firfl: phalanx from the palm of the feribed, the firft and fecond external interofiei perform, hand, or to keep it at a diflance therefrom. alternately the addudion and abdudion of the middle finThe fecond of thefe mufcles when there are three, or ger ; the third performs the abdudion of t'he ring-finger; the fecond portion of the firfl: when there are but two, that is, moves it toward the little finger. ferves to extend the fecond phalanx on the firft. The firft internal interofl’eus makes the abdudion of The third when there are three, or the fecond when the index, or movesdt toward the middle finger; the fethere are but two, extends the third phalanx on the fe- cond makes the addudion of the ring-finger, by moving cond. it likewife toward the middle finger; and the third perWhen they adf all together, they aflift each other by forms the addudion of the little finger, or moves .it tothe graduated infertions of their fmall fubaltern tendons. ward the middle finger. The thenar, by its infertion in the firft phalanx of the The ufe of the femi-interofleus indicis is to move the: thumb, ferves to draw it from the firft bone of the meta- firft phalanx of the index, more or lefs diredly, toward carpus, more or lefs diredtly, as one of its portions ads the great edge of the metacarpus, by removing it from more than the other, or as they both ad equally. the middle finger. This motion is not a true addudion By the infertion of the large portion in the bafis of of the index toward the thumb. the fecond phalanx, by the intervention of the fefamoid The lumbricales, by the union of their tendons with bone of the fame fide, it may bend this phalanx lateral- thofe of the interoflei, are coadjutors to thefe mufcles, ly on the firft, and thereby bring the thumb to a great- not only in the lateral motions of the four fingers, but er diftance from the index. alfo in bending and extending them. In the lateral moThe mefothenar moves the firft phalanx of the thumb tions, they co-operate according to their fituation-in each towards theJioilow of the hand, more or lefs obliquely, fubjed; and it is poffible that the variety of their inferas it ads either alone or with the large portion of the tions anfwer to that of the interoffei,-fo that the recithenar, or even with the antithenar. By its infertion procal co-operation continues ftill to be equal. in the fefamoid bone of the fecond phalanx, it likewife moves that phalanx on the firft, and thereby affifts the flexor longus. The Muscles uhich move the The antithenar moves the firft phalanx of the thumb Sect. IX.Os Fetmris upon the Pelvis. toward the firft bone of the metacarpus, and thereby preftes the thumb laterally againft the index. This motion becomes more or lefs oblique by the co-operation of PSOAS Jive LUMB ARTS INTERNUS. the mefothenar. is a long thick mufcJe fituated in the abdomen The hypothenar minor ferves to feparate the little fin- on This the lumbar region, adhering‘to the vertebra of the ger from the reft; which motion is commonly called ab- loins, from the pofterior part of the os ilium to the anduttion. It likewife keeps this finger feparated in all part near the thigh. fituations, that is, in all degrees of flexion or extenfion. terior It is fixed above to the laft vetebra of the back, and The interoflei may have two different ufes, according thofe of the loins, that is, to the lateral parts of to their different infertion, and the different fituations of totheailbodies of thefe vertebra, and to the roots >pf their the fingers in which they are inferted. apophyfes. The infertions in the bodies of In general, they aflift the extenfor conmmtmis by their tranfverfe the vertebra are infertions in the lateral angles of the rhomboidal fiflures; little tendinous. by a kind of digitations, and are very for thereby they ad like lateral ropes, which, together thence the mufcle runs down laterally over the with the tendons of the extenfor, ferve to extend the os From ilium, on one fide of the iliac mufcle, and pafles unthird phalanx of each finger. der the ligamentum Fallopti, between the anterior inferiBy the fame lateral infertions they perform the lateral of the os ilium, and that eminence which from motioui of the fingers, that is, they prefs them all clofe itsor fpine fituatioa may be termed iliojetlinea.,. Before