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Part Ii p2 A N A T O M Y. From their fize they are termed great, middle, [mail, long, broad, thin : From their figure, triangular, fca- Sect. II. The Muscles of the Abdomen. hnous^ fquare. See. From their direction, f.rait, oblique, tranfverfe . From their {■W.xxzxiO'a, fliperior, infe- By the mufcles of the abdomen, or lower belly, we rior, external. See. mean thofe which form principally , the fides or circumWith refpedt to their ftrudture, mufcles are either ference of that cavity. They are commonly ten in numfimple or compound. Simple mufcles- are thofe whofe ber, five on each fide £ eight whereof are very large, the flefhy fibres, or rather the fiefhy portions of their mo- other two very fmall. ving fibres, are all uniformly difpdfed, arid terminate in tendons lying either in a (trait or oblique line. OBLIQJJUS EXTERN US. Compound mufcles are thofe whofe flefhy fibres are difpofed obliquely in'feveral particular ranks, reprefent- The obliquus externus is a broad thin mufcle, flefiiy ing the fame number of fimple mufcles, with their fibres, on its upper and back-part, and tendinous on the antelying in oppofite directions. In proportion to the num- rior and greateft portion of the lower part. It reaches ber of thefe ranks or feries, the mufcle is faidto be more from half the lateral and inferior part of the thorax, to or lefs compounded, aimoft half the lateral and fuperior part of the pelvis; and Whefi the compbund mufcle is, made up of two fimple back-part of the regio lumbaris to the linea alba. mufcles only, thefe are fo difpofed as to reprefent a fea- fromIt the is fixed, by its upper part, to the ribs; by the ther, and the compound mufcle is from- thence termed lower, to the .os ilium, ligamentum Fallopii, and o§ pupeuniform. bis ; and, by the fore-part,' to the linea alba. The poSome are made up of two mufcles more or lefs, in a fterior portion next the vertebrae of the loins has comlateral fituation with refpect to each other, and united at monly no true mufcular inlertions. one extremity: others are made up of three or four'mufcles, fituated in the’fame manner ; and if they are united OBLIQJJUS INTERNUS. at that extremity which the,ancients called the head of the mufcle, they are called hicipites, tricipites, ^cc.-accord- The internal oblique is a broad thin mufcle like the ing to the number of tfiefe heads; but if they are joined former, having neatly the fame extent and infertions; at the other extremity, they are termed bicornes, tricor- that.is, in the lower ribs above ; in the crifta of the os nes, See. and ligamentum Fallopii, below; and in the linea The mufcles are fixed by their extremities to different ilium before: but it differs from it in this, that its lowparts, and in different places of the human body. The alba, er part is more flefny than the upper. , greateft jfart of them are inferted in bones alone. Some One portion of its lov/er extremity, which is entirely are fixed partly to bones, and partly to> cartilages; as is fixed, by very (hort tendinous fibres, in the thofe of the ear and nofe: fome partly to bones, and flefhy, middle fpace between o labia of the crifta oftis ilipartly to the integuments ; as feveral mufcles of the face. um, from the back-parrtheoftw'the tubefofity o! that crifta, The names taken from the conne&ions and infertions near the fymphyfis of the os facrum, all the way o^ mufclcs are generally of two kinds; one common, to the fuperior and anterior fpine ofaimoft the os ilium; fo and referred to fome confiderable part of the body; as that its infertion reaches farther back than that of the when we fay, the mufcles of the head, of the thorax, external oblique. abdomen, 6"c. ; the other proper, fpecifying more par- The fleftiy fibres thus fixed, run up firft a little obliqueticularly the infertions of each mufcle, as the maftoideus, ly from behind forward, and then this obliquity increafes fternormaftoideue, &c. as the fibres lie more anterioily, and they The general ufe of the mufcles is to move all the parts proporticnably crofs thofe of the fleftiy portion of the external oblique,' of the body, whether hard, foft, or fluid. Mod of the being afterwards inferted exterioiiy in the lower edges of hjrd and foft parts are mdved by thefe powers being fix- the cartilages of all the falfe ribs, and thofe of the two ed to them, and they move the reft without any fuch in- loweft true ribs; reaching to die extremity of the ca/tifertion. ' The aCtion of the mufcles in, general, confifts chiefly lago enfiformis. mufcle is likewife called obliquus, defeendens', for in the contraction or fhortening of their flelhy portion; theThis fame reafon that the former is termed ufeendens, ob.by which the extremities of the .mufcle are brought near- liquus inferior, and obliquus minor, becaufe it does not er to, each other, and confequently the parts are moved reach fo high, and is not quite fo large as the external to which tKefe extremities are fixed. The principal phenomena of mufcular aCtion are oblique. thefe The fiefiry portion appears harder and more fwellMUSCULI RECTI. ed in the time of action than of inaction, as may be readily perceived by touching it in both ftates: The hard- The redli are long narrow mufcles, thicker than the nefs of this (welling iucreafes in proportion as the mo- obliqui. They lie'near each other like fwo large bands, tion is continued, as is likewife evident by the touch; from the lower part of'the thorax, to the os pubis, the and it likewife increafes by merely adding to the weight linea alba coming between them. Their broadd^dimior refiftance of the part moved, though its (Ituation docs niihes, and their thicknefs increafes gradually from above jiot continue to be changed. downwaxd. . . » . The
