Page:Encyclopædia Britannica, first edition - Volume I, A-B.pdf/354

 Part VI. A N A T O M Y. The epiglottis is an elaftic cartilage, nearly of the figure of a purflain leaf, narrow and thick at the lower The LARYNX. part, thin and flightly rounded at the upper part, gently The larynx forms the protuberance in the upper and convex on the forefide, and concave on the backfide. anterior part of the neck, called commonly powum Adami. It is fituated above the anterior or convex portion of the It is chiefly made up of five cartilages, viz, Cartilago cartilago thyroides ; and its lower extremity is tied .by a thyroides, which is the anterior and largefl; cricoides, Ihort. pretty broad, and very ftrong ligament, to the the inferior, and bafls of the reft; two arytenoides, the middle notch in. the upper edge of that cartilage. It is pofterior and fmalleft ; and the epiglottis, which is above perforated by a great number of holes, fomething like all the reft. Thefe cartilages are connedled together by thole in the leaves of the hypericum, or St John’s ligaments, and they have likewife mufcles, glands, mem- Wort, w'hich are hid by the membranes that cover its branes, &c. belonging to them. two fides. The cartilago thyroidaea is large and broad, and folded The cartilago thyroides is connedted to the cricoides in fuch a manner as to have a longitudinal convexity on the by feveral Ihort ftrong ligaments, round the articulations forefide, and two lateral portions, v/hich maybe termed of the two inferior cornua, with the lateral articular furalee. The upper part of its anterior middle portion is faces of the cricoides. The apices of the fuperior corformed into an angular notch; the upper edge of each nua are fixed to the poftcrior extremities pf the great ala makes an arch; and, together with the middle notch, cornua of the os hyoides, by flender, round ligaments, thefe two edges referable the upper part of an ace of about a quarter of an inch in length. hearts. The thyroides is likewife conne&ed to the os hyoides The lower edge of each ala is more even, and the by a Ihort, broad, ftrong ligament, one end of which is pofterior edges ot both are veryfmooth, being lengthen- inferted in the fuperior notch of the cartilage, and the ed out both above and below by apoph’yies, which are other in the lower edge of the bafis of the bone. It has named the cornua of the thyroid cartilage. alfo two bgaments at the middle of the concave fide,^ The cricoid cartilage reiembles a thick, irregular which belong to the arytenoidaeae. ting, very broad on one fide, and narrow on the other; The cricoides is tied to the lower p^rt of the thyroides or it may be compared to a fmall portion of a thick tube, by a ftrong ligament; and by the ligaments already mencut horizontally at one end, and very obliquely at the o- tioned, to the inferior cornua of that cartilage. Its bather. It is diftinguilhed into a bafis and top, into an an- fis is fixed to the firft cartilaginous ring of tke trachea terior, poftcrior, and two lateral fides. The bafis is al- arteria, by a ligament exa&ly like thofe by which, the omoft horizontal, when we ftand ; and to this the afpera ther rings are connected together ; and the membranous artetia is connedted ; fo that the cricoides may be looked or pofterior portion of the trachea is likewife fixed to the upon as the upper extrer%ity of the trachea. pofterior part of the bafis of the cricoides. The pofterior portion of the cricoides is larger than The cartilagines arytenoidrea; are connected to the crithe reft, and its pofterior or convex fide is divided by a coides by ligaments, which furround their articulations longitudinal eminence or prominent line into diftinft fur- with the top of that cartilage. Anteriorly the bafis of faces, for the infertion of mufcles. The top is gently each arytenoides is fixed to one end of a iigamentary Hoped above this prominent line, and terminates on each cord, which by its other end is inferted about the middle fide by a kind of obtufe angle, formed between it and the of the concave fide of the anterior portion of the thyoblique edge of each lateral portion of this cartilage. roides. At their infertions in the thyroides, thefe two The whole pofterior fide is diftinguifhed into two la- ligaments touch each other, but a fmall fpace is left teral portions by two prominent lines, each of which between them, where they are fixed in the two aryteruns down almoft in a ftreight direction from the articu- noides, and they feem likewife to have a final! adhefioa lar furface at the top, a little below the middle of this to the top of the cricoides. This is what is called the fide, where it terminates in another articular line a little glottis. concave; and near thefe four articular furfaces there are Under thefe two ligamentary cords there are two ofmall tubercles. The two fuperior furfaces are for the thers, which run likewife from behind forward. The inarticulation of the cartilagines arytenoidsese ; and the two terftice between the fuperior and inferior cords on each inferior, for the articulation of the inferior cornua or fide form a tranfverfe fiffure, which is the opening of a appendices of the cartilago thyroides. fmall membranes bag, the bottom of which is turned The cartilagines arytenoidacse are two fmall, equal, fi- outward, that is, towardqhe ala of the thyroides. Thefe milar cartilages, which, joined together, refemble the two facculi are chiefly formed by a continuation of the fpout of an ewer, and they are fituated on the top of the internal membrane of the larynx, and the inner furface cricoides. In each, we may confiderthe bafis; cornua; of their bottom appears fometimes to be glandulous. two fides, one pofterior and concave, the other anterior On the anterior furface of the arytenoid cartilages, and convex; and two edges, one internal, the other ex- there is a fmall depreffion between th? bafis and the conternal, which is very oblique. The bafes are broad and vex upper part. This depreflion is filled by a glandulous thick, and have each a concave articular furface, by body, which not only covers the anterior furface of each arytenoides, but is likewife extended forward from the which they are joined 10 the cricoides. The cornua are bent backward, and a little toward bafis over the pofterior extremity of the neighbouring lieach other. gamentary cord. The 5oo