| XXX | (297) | XXX |
297' A N A T O M Y. Fart VI. branches or legs.are two, one long and one fliort. .The tremity of the long leg of the incus, fc-eing-articulated body is turned forward, the fhort leg backward, and the with each of thefe. In dry bones it is found very clofely connedled, fometimes to the llapes, fometimes to the long leg downward. The body of the incus is broader than it is thick. It incus, and might in that Hate be eafily miltaken for an ehas two eminences, and two cavities between them, much piphylis of either of thefe bones. in the fame manner as we fee in the crown of the firft The labyrinth is divided into three parts, the anterior, middle, and pollerior. The middle portion is termed grinders. The fhort leg is thick at its origin, and from thence veJUbulum the anterior, cochlea and the pollerior, the decreafing gradually, it ends in a point. It is fituated ho- labyrinth in particular, which comprehends the three fqrizontally, its point being turned backward, and joined micircular canals. The veltibulum is an irregularly round cavity, lefs to the edge of the mafloid opening of the tympanum. The long leg, viewed through the external auditory than the tympanum, and fituated more inward and a litpaffage, appears to be fituated vertically ; but if we look tle mere forward. 1 hefe two cavities are, in a manner, upon it either on the fore or backfide, we fee it is incli- fet back to back, with a common partition-wall between ned, the extremity of it being turned much more'inward, them, perforated near the middle by the feneltra ovalis, than the mot or origin. The point of the extremity is by which the cavities communicate with one another. a little flatted, and bent inward like a hook, and fomer The cavity of the vellibulum is likewife perforated by times a little hollowed like a kind of ear-picker. feveral other holes; on the outfide, or towards the tymThe malleus or hammer is a long bone, with a large panum, by the fenellra rotunda; on the backfide, by the head, a fmall neck, an handle, and two apophyfes, one five orifices of the femicircular canals; on the lower part of the forefide, by two holes, which are the entry in the neck, the other in the handle. The top of the head is confiderably rounded, and from of the cochlea; and on the fore-fide, towards the interthence it contrafts all the way to the neck. Bpth head nal meatus auditorius, oppofite to the fenellra ovalis, by and neck are ia an inclined fltuation, and the eminences a great many very fmall holes for the paflage of the and cavities in it anfwer to thofe in the body of the nerves. incus. The femicircular canals are three in number, one verThe.handle is looked upon by fome as one of the a- tical and fuperior, one vertical and polfeiior, and one hopophyfes of the malleus; and in that cafe, it is the great- rizontal. The fuperior vertical canal is fituated tranfell of the three. It forms an angle with the neck and verfely with refpe<3 to the apophyfis petrofa, the convex head, near which it is fomething. broad and flat, and de- fide or curvature of it being turned upward, and-the excrpafes gradually toward its extremity. tremities downward, one inward, the other outward. The apophyfis of the. handle, termed by others the The pofeerior vertical canal lies parallel to the length of fmall or fhort ttppphyfis of the malleus, terminates the the apophyfis, the curvature being turned backward, and angle already mentioned, being extended towards the the extremities forward, one upward, the other downneck, and lying in a llraight line with that fide or border ward ; and the fuperior extremity of this canal meets and of the handle which is next it. lofes itfelf in the internal extremity of the former. The The apophyfis of the neck, called alfo aptphyfu gra- curvature and extremities of the horizontal canal are alcilis, is in a natural Hate very long, but fo {lender with- mclt on a level; .the curvature lying obliouely backward, al, that it is very eafily broken, efpecially when dry; it and the extremities forward, ending under thofe of the arifes from the neck, and fometimes appears much longvertical canal, but a little nearer each other ; er than it really is, by the addition of a fmall dried ten- fupetior and. the inner being almoll in the middle fpace, between don (licking to it. the extremities of the pollerior vertical canal. The llapes is a fmall hone, very well denominated horizontal canal is generally the leaf! of the three; from the refemblance it bears to a llirrup. It is divided theThe pollerior vertical is often, and the fuperior vertical into the head, legs, and bafis. fometimes’ the greatell; all the three canals are larger The head is placed upon a fhort flatted, neck, the top a femicircle, forming nearly three quadrants; they ©f it being fometimes fiat, fpmetimes a little hollow. than are broader than in the middle. Thefe The two legs taken together, form an arch, like that orifices openatintothetheorifices back-fide of the vellibulum, being of a (lirrup, in the concave fide of which is a groove, but five in number, fo that in the pollcrior part of the which runs.,through their whole length. One leg is long- vellibulum, two appear towards the infide, and three er, more bent, and a little broader than the other. towards the outfide. The bafrs refembles that of a llirrup, both,in its oval The cochlea is a fort of fpiral (hell, with two dufts, (hape, 'and union with the legs, except that it is not per- formed in the anterior part of the apophyfis petrofa, in forated as the llirrups now are, but fohd, like thofe of fome meafure refembling the fliell of a fnail. The parts the ancients. Round its circumference, next the legs, be diltinguilhed in it, are the bafis, the apex, the fpirnl is a little border, which makes that fide of the-bafis appear tolamina, or halffeptum, by which its cavity is divided ina little hollow. The other fide is pretty fmooth, and to two half-canals
- the fpindle round which the cochlea
one half of the circumference is fomething more curve turns ;. and lallly, the orifices and union of the two duds. than the other. The bafis is turned inward, toward the interThe orbicular or lenticular bone is the fmallell bone in nal foramen auditorium,diredly the apex outward, and the axis the body. It lies between the head of the llapes and ex- of the fpindle is nearly horizontal. Vol. I. Numb. 13. 34F The
