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 Part I. A N A T O M Y. 185 far backwards. In performing this, the rotula back than the Internal malleolus, and in an oblique di- fmooth pulled down by the tibia. When the leg is to be reftion, obliges ns naturally to tarn the fore-part of the isextended, the rotula is drawn upwards, confequently foot outwards. At the lower internal part of this protibia forwards, by the extenfor mufcles ; which, by cefs, a fpongy cavity for mucilaginous glands may be re- the of the protuberant joint, and of this thick bone marked ; from its point, ligaments are extended to the a- means its ligament, have in effe<5t the chord, with which flragalus, os calcis, and os naviculare, bones of the foot; with aft, fixed to the tibia at a confiderable angle, thereand from its infide, Ihort ftrong ones go out to the altra- they fore aft with advantage; but are reftrained from pulling galus. On the back-part of it, a finuofity is made by the the farther than to a ftreight line with the thigh, by tendons of the peronaei mufcles.—When the ligament the leg part of the crofs ligament, that the body extended over thefe tendons from the one fide of the mightpofterior by a firm perpendicular column : For depreflion to the other is broke, (Iretched too much, or at this betimefupported and leg are as little moveable in a made weak by a fprain, the tendons frequently ftart for- rotatory way,theorthigh to either fide, as if they were one conwards to the outhde of the fibula. bone. But when the joint is a little bended, The conjundtion of the upper end of the fibula with tinued rotula is not tightly braced, and the pofterior ligathe tibia is, by plain furfaces, tipped with cartilage; and, the at its lower end, the cartilage feems to glue the two bones ment is relaxed; therefore this bone may be moved a littogether, not, however, fo firmly in young people, but tle to either fide, or with a fmall rotation in the fuperfithat the motion at the other end of fuch a long radius is cial cavities of the tibia; which is done by the motion of the external cavity backwards and forwards, the inVery obfervable. The principal ufe of this bone is to afford origin and ternal ferving as a fort of axis. Seeing then one part of infertion to mufcles; the diredlion of which may be a the crofs ligament is fituated perpendicularly, and the little altered, on proper occafions, by its upper part pofterior part is ftretched obliquely from the internal /huffiing backwards and forwards. It likewife helps condyle of the thigh outwards, that pofterior part of to make the articulation of the foot more fecure and the crofs digament prevents the leg’s being turned at all inwards; but it could not hinder it from turning out•firm. Rotula is the fmall flat bone fituated at the fore-part wards almoft round, was not that motion confined by the •of the joint of the knee. Its (hape refemhles the lateral ligaments of this joint, which can yield little. common figure of the heart with its point downwards.— The Foot is divided into three parts, viz. tarfji, The anterior convex furface of the rotula is pierced by a vietaiarfus, and toes : In the defeription of which, the great number of holes, into which fibres of the ftrong li- broad of the foot fhali be called fuftrior; the foie, ingament that is fpread over it enter. Behind, its fur- ferior ; the fide on which the great toe is, internal; that face is fmooth, covered with cartilage, and divided by a where the little toe is, external middle convex ridge into two cavities, of which the ex- The tarfus confifts of feven fpongy bones ; to wit, the ternal is largeft, and both are exa<5tly adapted to the pul- ajlragalus, os calcis, naviculare, cuboides, cuneiform? ley of the os femoris, on which they are placed in the externut/i, cuneiforme medium, and cuneiforms inmoft ordinary unftraining poftures of the leg; but when ternum. •the leg is much bended, the rotula defcends far down The aftragalus is the uppermoft of thefe bones. on the condyles; and when the leg js fully extended, The os calcis is below the aftragalus, and is confiderably •the rotula rifes higher, in its upper part, than the pulley prominent backwards beyond the other bones, to form of the thigh-bone. The plain fmooth furface is fur- the heel. The os naviculare is in the middle of the rounded by a rough prominent edge, to which the capfu- internal fide of the tarfus. The os .cuboides is the lar ligament adheres :—Below, the point of the bone is molt external of the row of four bones at its fore-part. fcabrous, where the ftrong tendinous ligament from the The os cuneiforme externum is placed at the infide tubercle of the tibia is fixed.—The upper horizontal part of the cuboid. The cuneiforme medium is between of this bone is flatted and unequal, where the tendons of the external and internal cuneiform bones, and the interthe extenfors of the leg are inferted. nal cuneiform is put at the internal fide of the foot. The fubftance of the rotula is cellular, with very thin In the defeription of thefe bones, let it be obferved, external firm plates: But then thefe cells are fo fmall, That where-ever a ridge is mentioned, without a partiand fuch a quantity of bone is employed in their forma- cular ufe afligned, a ligament is underftood to be fixed to tion, that fcarce any bone of its bulk is fo ftrong. Be- it: or where a fpongy rough cavity, depreflion, or ^pffa, fides, it is covered all over with a thick ligament, to con- is remarked, without naming its ufe, a ligament is innetfl its fubftance, and is moveable to one fide or other; ferted, and mucilaginous glands are lodged. therefore is fufficiently ftrong to refill the ordinary aftions The upper part of the aftragalus is formed into a large of the large mufcles that are inferted into it, or any com- fmooth head, which is flightly hollowed in the middle; mon external force applied to it. and therefore refembles a fuperficiai pulley, by which' it The parts which conftitute the joint of the knee being is fitted to the lower end of the tibia. The iiternal now defcribed, let us examine what are its motions, and fide of this head is flat and fmooth, to play on the interhow performed. The two principal motions are flec- nal malleolus. The external fide has alio inch a furtion and extenfion. In the former of thefe, the leg face, but larger, for its articulation with the external may be brought to a very acute angle with the thigh, by Round the bafe of this head there is a the condyles of the thigh-bones being round and made malleolus. rough foffa; and, immediately before the head, as alfo 3 3A below
 * Von. I. No. 8.