Page:Encyclopædia Britannica, first edition - Volume I, A-B.pdf/347

 Part VI. ANA T O M Y. comprehend-the whole fpace betweeri the external at the union of the points, or at the extremities of the rofe, nares and pofterior openings immediately - above the two tarli. of the palate', from whence thefe cavities reach up* This mufcle is divided into four portions, whereof the arch as far as the lamina cribrofa of the os cthmoides, firft is that which furrounds the orbit. The fecond ward where they communicate forward with the finus fronportion is that which Ties between the upper edge of the tales, with the finus fphenoidales. Laorbit and the globe of the eye, and which covers the in- terally,andthefebackward cavities are bounded on the infide by the ferior edge of the orbit below, fome of its fibres being feptum oarium,-a.nd on the outfide, or .that next the cheeks, fixed to both edges of the orbit. conchae, between which they, communicate with Tire third portion feems to belong more particularly by the Aims maxillaris. to the palpebrse, and thegreateft part of it is Ipent in the theThe particular fituation of thefe cavities deferves our palpebrs. fuperior. The fibres of this portion meet at attention. The bottom of them runs direXly backward, the two angles of the eye, where they, appear to make fo that a ftreight and pretty large llilet may eafily be very acute inflexions without any difcontinuation. from the external nares, under the'gi tat apophyThe fourth portion is an appendix to the third, from fispafied the occipital bone. The openings of the maxillawhich it differs chiefly in this, that its fibres do not ry offmufes are nearly oppofite to the upper edge of the reach to the angles, and form only fmall arches, the ex- offa malarum. The openings of the frontal linufes are tremities of which terminate in each palpebra. or Jefs oppofite to, and between the pulleys or rings All thefe different portions of the orbicular mufcle ad- more trochleares; and by thefe marks the fituhere to the fkin, which covers it from the upper part of ofationtheofmufeuli all the other parts may be determined. the nofe to the temples, and from the fapercihum to the upper part of the cheek. , When they contraff, feveral The inferior portion of the external nofe is compofed wrinkles are formed in the fkin, which vary according to of feveral cartilages, which are commonly five in number, and of a pretty regular figure. The reft are only the different direXions of the fibres. additional, fmaller, more irregular, and the number of more uncertain. Of the five ordinary cartilages, The Uses of the Eye, and ofits appendages, ingeneral. them one is fituated in the middle, the other four laterally. Every body knows that, the eye is the organ of vi- 7 he middle cartilage is the tnoft confiderable, and fupfion. The tranfparent parts of the globe modify the ports the reft, being conneXed immediately to the bony rays of light, by different refraXions ; the retina and parts ; but the other four are conneXed to the middle carchoroides receive the different impreffions of thefe rays; tilage, and to each other, by means of ligaments. and the optic nerve carries thefe impreflions to the brain. The fub-feptum, or portion under the feptum narium, is When objeXs are at a great diftance or obfcure, the pu- a pillar of fat applied to the inferior edge of the cartilagipilla is dilated; and it is contraXed when objeXs are nous partition, in form of a foft moveable appendix. The rear, or placed in a great light. The mufcles of the thicknefs of the alae narium, and efpecially that of their globe of the eye and of the palpebrse perform the mo- lower edges, is not owing to the cartilages, which are tions already defcribed. very thin, but to the fame kind of folid fat with which The glandula lachrymalis continually moiftens the fore- thele cartilages are covered. The great cartilage is impart of the globe of the eye ; and the lachrymal ferum is moveable by reafon of its firm connexion to the bony equally fpread over that globe by the motions of the fu- parts of the nofe; but the lateral cartilages are moveyerior palpebra, the inner furface of which is in a fmall able, becaufe of their ligamentary connexions, and they ■neafure villous.. The union of the two palpebne direfts are moved in different manners by the mufcles belonging this ferum towards'the punXa lachrymalia; and the unXu- to them. ous matter, difeharged through the foramina ciliaria, The external nofe is covered by the common integuhitjders it from running out between the palpebrae. The ments, the ikin, epidermis, and fat. Thofe w'hich colarge fize and vifeid furface of the caruncula prevents it ver the tip of the nofe and alffi narium are a great numfrom running beyond the punXa, and thus forces it into ber of glandular bodies, called glandula febacea, the them. The fupercilia may hinder fweat from falling on the contents of which may eafily be fqueezed out by the eyes. The fuperior cilia, which are longer than the in- fingers. mufcles are commonly reckoned to belong to the ferior, may have the fame ufe; and they both ferve to Six two reXi, called alfo pyrawidales or triangulares; prevent duft, infeXs, &c. from entering the eyes when nofe; two obliqui, orlaterales; and two tranfverfi, or tnyrtithey are only a little open. formes. The nofe may alfo be moved in fome meafiure hy the mufcles of the lips, which in many cafes beccrnfe alf.ftants to the proper mufcles of this organ. Sect. VI. The Nose. The mufculus pyramidalis, or anterior, on each fide, is inferred by one extremity in the fynarthrofis of the os The bones of the nofe have already been defcribed in fronds and offa nafi, where its flefhy fibres mix with the futures of the bones of the head, thofe of the mufeuli frontales and faperciliares. It is The foft parts are the integuments, mufcles, facculus very flat, and runs down on the fide of the nofe, increalachrymalis, membrana pituitaria, and hairs of the nares. fing-gradually in breadth, and terminating by an apoueuThe internal nares, or the two cavities of the rofis, which reprefeats the bafis of a pyramid, and is inVou. I. No. 13. 3 4E ferted