LUNG 3. 



middle collo-tranfverfiil iierarr.cnts, it may be eonfidered as 

 forming a kind of fibrous capfule. 



The inter-articular lifjament does not exill in the joints 

 of the firil, eleventh, and twelfth ribs. It is a more or 

 lefs thick fibrous fafcicidus, of a flattened figure, fixed on 

 one fide to the prominent angle of the head of the rib, and 

 on the other to the correfponding depreffion of the cavity 

 in which it is received. It feparates the two fynovial mem- 

 branes from each other, and is continuoiis with the fibro. 

 cartilaaje, as we may perceive by fawing the joint acrofs, fo 

 as to divide it into a fuperior and an inferior half. 



The fynovial membranes are double in the joints that 

 pofTefs the ligament lad defcribed ; but in the others there 

 ,is only a fingle one, covering the whole extent of the cor- 

 refpondmg articular furfaces, and reflefted from the one to 

 the other. Where there are two, each capfule belongs to 

 its correfponding upper or lower half of the arti:ulatio:!, 

 and is feparated from the other by the inter-articular liga- 

 ment. Thefe membranes are not clearly marked, do not 

 exhibit the ufual polifh on their furface, contain a remark- 

 ably fmall quantity of fynovia, and occupy often a very 

 fmall fpace on account of the great fize of the inter-articular 

 ligament. The latter is fometimes fo thick, that it may 

 almoll be doubted, wliether the joint poflefles any fvnovial 

 membrane ; in other inftances, however, tlicfe membranes 

 are very dilb'ntl. Although the bones are held together 

 almoft as clofely as at the anterior articulations between the 

 cartilages and the fternum, the joint is not fo frequently loil 

 in the old fubjeil". Yet anchylofis does fometimes occur ; 

 and this is a charatier dillinguifiiing it from joints where the 

 membrane is clearly marked, which may be anchylofed 

 from accident or difcafe, but hardly ever undergoes this 

 change in the natural progrefs of offification. 



The C'l/lo-tran/ivrfa/ ■j.rUtsul^itions are formed by a fmall 

 fynovial cavity, a pollcrior, a middle, and an inferior collo- 

 tranfverfal ligament. The latter does not belong to the 

 tubercle and procefs which are contiguous : but extends 

 from the procefs to the upper edge of the rib immediately 

 below. The potterior ligaTi^nt arifes fioni the end of the 

 procefs, paffes nearly horizontally outwards, and is inferted 

 into the rough eminence of the tubercle of the rib. Its 

 fibres are parallel and clofe, form a very diltin£t fafciculus 

 nearly quadrilateral in its figure, correfpond behind to the 

 rhufcles contamed in the excavations on the fides of the 

 fpinous proceffes, and in front to the articulation. The 

 middle ligament is a coUettion of irregular reddifh fibres, 

 rather cellular than ftridly ligamentous, placed between the 

 fr^mt of each tranfverfe procefs, and the correlponding 

 part of the rib. When we forcibly feparate thefe parts, 

 we dillinguifli the fibres which are torn by the feparation : 

 to !ee them entire we fhould faw through the procefs and 

 rib in their connefted ftate. The inferior ligament is a 

 diflinft fi«rous fafciculus, compofed of numerous (Irong 

 and parallel fibres. It arifes from the root of the tranf- 

 verfe procefs, paffes obliquely to the upper edge of the rib 

 immediately below, and is inferted near the vertebral ex- 

 tremity. The fird and the laft ribs do not pofTefs it. It is 

 covered in front by the intercollal veffels and nerves, be- 

 hind by the longiffimus dorfi : on the outfide it is continu- 

 ous, by means of a tiiin aponeurofis, with the intercollal 

 m'lfcle, and it completes on the infide a fmall cellular fpace 

 traverfed by the polterior branch of the nerves. Between 

 this fpace and the vertebral column there is commonly a 

 fmall fibrous fafciculus, arifing from thebafis of the procefs, 

 and attached to the articular extremity of the rib below, 

 where it is united to the upper part of the radiated liga- 

 ment. The two cartilaginous furfaces, of the tranfverfe 

 Vol. XXI. 



procefs and the tubercle of the rib, are covered by a fmill 

 fynovial membrane, which is loufcr, contains more fynovia, 

 and is always more dillinct than that of the preceding y^i.i'. 

 Hence it never becomes anchylofed by the mere progrefs of 

 age. 



/Inltr'ior jlrticulalions of the Chejl. — Thefe are not formed 

 by the bony portions of the ribs, but by a feries of cartilages 

 terminating them : the fevcn fuperior of thefe are joined to 

 the flernum, while the five inferior, connected to each other, 

 have no other kind of connection. Thefe cartilages muft, 

 be defcribed before we fpeak of the articulations. They 

 are not uniform in their length, breadth, and direction. 

 That of the firft rib is very (liort ; the fucceeding onei in- 

 creafe in length as far as the laft of the true ribs. Thofe of 

 the falfe ribs again become (horter and fliorter, fo that it is 

 fcarcel) perceptible in the lalL The firft is the Tjroadeft, 

 and they become narrower as they are placed lower down. 

 The breadth of the two firft is nearly uniform throughout ; 

 it diminillies in the others from the coftal towards the oppo- 

 fite extremity. This diminution, however, is not regular in 

 the fixth, feventh, and eighth, which are confiderably in- 

 creafed in breadth, where they are joined to ea;;h other. The 

 firft cartilage is a little oblique from above downwards ; fo 

 that tlie angle formed between it and the fternum is acute 

 above and obtufe below ; the fecond is nearly horizontal, 

 and follows the fame direction as the rib to which it be- 

 longs. The following cartilages of the true ribs are more 

 oblique from below upwards, and more nianifcftly curved 

 where they arife from the ribs in proportion as they are 

 lower. At this curvature the ribs and their cartilages take 

 oppofite direftions : the firft defccnd from the fpine, the 

 others afcend to the fternum. This curvature is diminiftied a 

 little in the firft of the falfe ribs, where, however, it is 

 ftill very confiderable, and decreafes fuccefiivcly to the laft, 

 in which the cartilage follows the direction of the bone. 



The general figure of the cartilages correfponds to that 

 of the bones to which they are connected. The furface of 

 the body is rather unequal externally, or on the front, 

 nightly convex in moft, covered by the peftoralis major 

 above, by the obliqnus externus and rectus below. The 

 firft gives attaclnnent to the cofto-clavicular ligament. Be- 

 hind or on the infide it is flightly concave, and correfponds 

 in the firft five or fix to the pleura and triangularis fterni, 

 to the tranfverfus abdominis in the fucceeding ones. Tiie 

 upper edge is more or lefs concave, and the lower convex : 

 they afford attachment to the intercoftal mufcies, and form 

 a continuation of the intercoftal ipaces, which, as well as 

 the mufcies of the fame name, become narrower in pro- 

 portion as they are lower. Thofe between the fixth and 

 ieventh cartilages, and between the latter and the eighth, are 

 interrupted by imall articulations, formed by the contiguous 

 cartilaginous furface.'. 



Each cartilage has an external or coftal and an internal 

 extremity, which may be alTo called fternal in the fevcn 

 firft. The former confifts of a fmall convex and unequal 

 furface intimately united to the correfponding concavity in 

 the extremity of the rib. The latter has in the true ribs 

 a fmall articular furface of a convex figure, adapted to tlie 

 hollow of the fternum, in which it is received. In the three 

 firft falfe ribs this extremity is elongated, fituated immedi- 

 ately under the cartilage above it, and united to it : in the two 

 laft it is feparated from the cartilage above by a marked 

 interval. 



In refpeft to their ftrufture, the cartilages of the ribs 



have a great analogy to thofe of the larynx. Both are 



very denfe and compaft, exhibit, at firft view, no marks of 



organization, although they poffefs really a peculiar llruc- 



.\. K ture, 



