Page:Encyclopædia Britannica, first edition - Volume I, A-B.pdf/226

 Part T. i86 A N A T O M Y. below its internal fmooth furface, we find a confiderable ed for the tendon of the flexor digitorum profundus. rough cavity. The lower furface of this bone is prefled flat at the The lower furface of the aftragalus is divided by an back-part, by the weight of our bodies; and immediirregular, deep, rough fofla; which, at its internal end, ately before this plane, there are two tubercles, from is narrow, but gradually widens, as it ftretches obliquely the internal of which the mufculus abdu&or pollicis, outwards and forwards.—The fmooth furface, covered flexor digitorum fublimis, as alfo part of the aponeurofis with cartilage, behind this fofi'a, is large, oblong, ex- plantaris, and of the abdudtor minimi digiti, have their tended in the fame oblique fituation with the fofla, and origin ; and the other part of the abdudlor minimi digiti concave, for its conjundion with the os calcis. The and aponeurofis plantaris, rifes from the external. back-part of the edge of this cavity is produced into two Before thefe protuberances this bone is concave, for fliarp-pointed rough procefles, between which is a depref- lodging the flexor mufcles ; and at its- fore-part we may fion, made by the tendon of the flexor pollicis longus. oblerve a rough depreflion, from which, and a tubercle —The lower furface before the fofla is convex, and com- behind it, the ligament goes out that prevents this bone pofed of three diftinft fmooth planes. The long one to be Separated from the os cuboides. behind, and the,exterior or ftiortefl, are articulated with The fore-part of the os calcis is formed into an obthe heel-bone ; while the internal, which is the moft con- long, pulley-like,, fmooth furface, which is circular at vex of the three, reds and moves upon a cartilaginous its upper external end, but is pointed below. This ligament, that is continued from the calcaneum to the os fmooth furface is fitted to the os cuboides. Though the furfaces by which the aftragalus and os fcaphoides. The fore-part of this bone is formed into a convex calcis are articulated, feem fit enough for motion; yet oblong fmooth head, which is received by the os navi- the very ftrong ligaments by which thefe bones are conculare.— Round the root of this head, efpecially on the neifted, prevent it, and render this principal part of our bafe, which refts on the ground, to wit, the os calcis, upper furface, a rough fofl’a may be remarked. The aftragalus is articulated above to the tibia and fi- firm. bula, which together form one cavity. Though, in this Os naviculare, is fomewhat circular.—It is formed inarticulation, the bones have prominences and cavities fo to an oblong concavity behind, for receiving the anterior fmall, as might allow motions in all directions; yet the head of the aftragalus.—On the upper furface, there is fleCtion and extenfioa are the molt confiderable, the o- a rough folfa.—Below, the os naviculare is very unequal ther motions being confined by the malleoli, and by the and rough ; but hollow for the fafety of the mufcles.— Itrong ligaments which go out from the points of thefe On its infide, a large knob rifes out, from which the procefles to the aftragalus and os calcis. The aftragalus abduiftor pollicis takes in part its origin, the tendon of is joined below to the os calcis; and before, to the os the tibialis pofticus is inferted into it, and to it two reuaviculare, in the manner to be explained when thefe markable ligaments are fixed; the firft is the ftrong one, formerly mentioned, which fupports the afti agalus; the bones are defcribed. Calcaneum is the largeft bone of the feven.'—Behind, fecond is ftretched from this bone obliquely crofs the it is formed into a large knob, commonly called the heel: foot, to the metatarfal bones of the middle toe, and toe next to the little one.—On the outfide of the The furface of which is rough behind, where the tendo osof the Achillis is inferted into it; and above, it is hollow and naviculare, there is a femicircular fmooth furface, fpongy. Farther forwards, on the upper furface of the where it is joined to the os cuboides.—The fore-part of calcaneum, there is an irregular, oblong, fmooth con- this bone is all covered with cartilage, and is divided vexity, adapted to the concavity at the back-part of the into three fmooth planes, fitted to the three ofia cuneiaftragalus : And beyond this a narrow fofla is leen, which formia. os naviculare and aftragalus are joined as a ball divides it from two final! concave fmooth furfaces, that andThe focket, and the.naviculare moves in all directions in are joined to the fore-part of the aftragalus.—Behind turning the toes inwards, or in raifing or deprefling either the pofterior of thefe fraooth furfaces, which is the largeft, a fmall finuofity is made by the tendon of the flexor fide of the foot, though the motions are greatly reftraindigitorum longus ; at the fore-part of which a fmall ed by the ligaments which conned this to the other bones tarfus. rough protuberance appears, that gives rife to the muf- of Osthecuboides is a very irregular cube. Behind, it culus extenfor digitorum brevis. formed into an oblong unequal concavity, adapted T'he external fide of this bone is flat, with a fuperfi- isto the of the os calcis.—On its internal fide, cial fofla running horizontally, in which the tendon of there isfore-part a fmall femicircular fmooth cavity, to join the os the mufculus peronseus longus is lodged.—The internal naviculare.—Immediately which, an oblong fmooth fide of the heel-bone is hollowed, for lodging the origin plane is made by the os before externum. Beof the mafia cornea Jac. Sylvii, and for the fafe paflage low this, the bone is hollowcuneiforme rough.—On the internal of tendons, nerves, and arteries.—Under the fide of the fide of the lower furface, a and round protuberance and fofla internal fmooth concavity, a particular groove is made are found, where the mufculus adduCtor pollicis has its by the tendon of the flexor pollicis longus; and from On the external fide of this fame furface, there the thin protuberance on this internal fide, the cartilagi- origin. nous ligament that fupports the aftragalus, goes out to is a round knob, covered with cartilage; immediately the os naviculare; on which ligament, and.on the edge before which, a fmooth fofla may be obferved, in which of this bone to which it is fixed, the groove is form- the tendon of the peronseus primus runs obliquely crofs