Page:Encyclopædia Britannica, first edition - Volume I, A-B.pdf/224

 1^4 A N A T O M Y. Part I. cartilages are not allowed to change place far ; while the of this end of the tibia has a rough irregular femilunar narrow ends of the cartilages, becoming almoft ligaments, cavity formed in it, for receiving the lower end of the fiare fixed at the infertion of the ftrong crofs ligament in- bula. The pofterior fide has two lateral grooves, and to the tibia, and feem to have their fubilance united with a fmall middle protuberance. In the internal depreilion, it; therefore a circular hole is left between each cartilage the tendons of the mufculus tibialis pofticus, and flexor and the ligament, in which the moft prominent convex lohgus, are lodged; and in the external, the part of each condyle of the thigh-bone moves. The digitorum tendon of the flexor longus pollicis plays. From the circumference of thefe ca.vities is rough and unequal, for middle protuberance, ligamentous ihsaths go out, for the firm connedion of the ligaments mf the joint. Im- tying down thefe tendons. mediately below the edge, at its back-part, two rough Fibula is the fmall long bone, placed on the outfide flatted protuberances ftand out: Into the internal, the of the leg, oppofite to the external angle of the tibia ; tendon of the femimembranofus mufcle is inferred ; and the fhape of it is irregularly triangular. a part of the crofs ligament is fixed to the external. The head of the fibula has a fuperficial circular cavity On the outfide of this lad tubercle, a fmooth flightly- formed on its infide, which, in a recent fubjed:, is coverhollowed furface is formed by the adion of the poplitaeus ed with a cartilage, but fo clofely connedted to the tibia .mufcle. by ligaments, as to allow only a fmall motion backwards Below the fore-part of the upper end of the tibia, a and forwards.—This head is protuberant and rough on its confiderable rough protuberance rifes, to which the ItrOng outfide, where a ftrong round ligament, and the mufculus tendinous ligament of the rotula is fixed. On the in- biceps, are inferted ; and, below the back-part of its internal fide of this, there is a broad, fcabrous, fiightly- ternal fide, a tubercle may be remarked, that gives rile hollowed furface, to which the internal long ligament of to the ftrong tendinous part of the folasus mufcle. the joint, the aponeurofis of the vaftus internus, and the The body of this bone is a little crooked inwards and tendons of the feminervofus, gracilis, and fartorius, are backwards, which figure is owing to the adtions of the fixed.—Below the external edge of the upper end of the mufcles ; but is (till further increafed by nurfes, who ofttibia, there is a circular flat furface, covered, in a recent en hold'children carelefsly by the legs. The ftiarpeft fnbjed, with cartilage, for the articulation of the fibula; angle of the fibula is forwards, on each fide of which •—between.which and the anterior knob, there is a rough the bone is confiderably, but unequally, deprefled by the hollow, from which the tibialis anticus, and extenfor di- bellies of the feveral mufcles that rife from, or aft upon gitorum longus, take their origin.—From the fmooth flat it; and, in old people, thefe mufcles make diftinft finuofurface, a ridge runs obliquely downwards and inwards, fities for themfelves. The external furface of the fito give rife to part of the folseus, tibialis pofticus, and bula is depreffed obliquely from above downwards and flexor digitorum longus, and infertion tp the aponeurofis backwards, by the two peronsei. Its internal furface of the femimembranofus which covers the poplitseus, and is unequally divided into two narrow longitudinal planes, to fome of the external fibres of this laft named mufcle. by an oblique ridge extended from the upper part of the —At the infide of this ridge an oblique plain furface is ' anterior angle, to join with the lower end of the interleft, where the greateft part of the mufculus poplitaeus nal angle. To this ridge the ligament ftretched between is inferted.—The remaining body of the tibia is triangu- the two bones of the leg is connefted. The anterior gular.—The anterior angle is very (harp, and is com- of the two planes is very narrow above, where the exmonly called the fpine or Jhin. This ridge is not tenfor longus digitorum, and extenfor longus pollicis, a ftreight; but turns firft inwards, then outwards, and rife from it; but is broader below, where it has the print laftly inwards again.—The plain internal fide is fmooth of the nonus Vefalii.—The poftericr plane is broad and and equal, being little fubje&ed to the aftions of muf- hollow, giving origin to the larger (hare of the tibialis cles ; but the external fide is hollowed above by the tibi- pofticus.—The internal angle of this bone has a tendialis anticus, and below by the extenfor digitorum longus, nous membrane fixed to it, from which fibres of the flexor and extenfor pollicis longus.—The two angles behind digitorum longus take their rife.—The pofterior furface thefe fides are rounded by the adtion of the mufcles ;— of the fibula is the plaineft and fmootheft, but is made the pofterior fide comprehended between them is not fo flat above by the folasus, and is hollowed below by the broad as thofe already mentioned, but is more oblique flexor pollicis longus.—In the middle of this furface the and flatted by the aflion of the tibialis pofticus and flexor canal for the medullary veflels may be feen flanting downdigitorum longus.—Some way above the middle of the wards. bone, the internal angle terminates, and the bone is The lower end of the fibula is extended into a fpongy made round by the preflure of the mufculus folxus.— oblong head, on the infide of which is a convex, irreNear to this, the. paflage of the medullary veflels is feen gular, and frequently a fcabrous furface,,that is receiflanting obliquely downwards. ved by the external hollow of the tibia, and fo firmly The lower end of the tibia is made hollow, but fo as joined to it by a very thin intermediate cartilage and ftrong a ftnall protuberance rifes in the middle.—The internal ligaments, that it fcarce can move.—Below this, the fifide of this cavity, which is fmooth, and, in a recent bula is ftretched out into a coronoid procefs, that is fubjedt, is covered with cartilage, is produced into a con- fmooth, covered with cartilage on its internal fide, and fiderable procefs, commonly named malleolus internus is there contiguous to the outfide of the firft bone of the the point of which is divided by a notch, and from it li- foot, the aftragalus, to fecure the articulation. This gaments are fent out to the foot. The external fide precefs, named malleolus externus, being fituated farther back