1032 



THORAX. 



to a greater or less extent in the other car- 

 tilages, and it is apparent in those of the 

 false, later than in those of the true ribs. 



These observations apply to the male body ; 

 for in the female the process of ossification 

 does not affect the cartilages until old age has 

 arrived, and it always affects a comparatively 

 small number of cartilages, even if it should 

 happen to extend beyond the 1st, which com- 

 monly is not the case. 



Of the ligaments of the ribs. The liga- 

 ments of the ribs may be divided into three 

 sets, those which connect them, 1st, with the 

 bodies of the vertebra ; 2ndly, with the trans- 

 verse processes, and Srdly, with the sternum. 

 The rib is connected with the bodies of two 

 vertebrae (excepting those specified above) 

 forming with each a joint lined with synovial 

 membrane, and held in place by the following 

 ligaments : 



1st. With the bodies of the vertebra. Costo- 

 vertebral ligaments, (lig. capitulorum costarum). 

 These consist, 1st, of an anterior ligament 

 which connects the head of each rib with the 

 sides of the bodies of the vertebrae. Its fibres, 

 flat and radiated, are divided into three bundles, 

 of which the middle one passes horizontallytfor- 

 wards upon the corresponding inter- vertebral 

 cartilage, whilst the superior ascends to the 

 body of the vertebra above it, and the inferior 

 descends to that below. From the divergence 

 of its fibres this is usually called the stellate 

 ligament. 2ndly, of an inter-articular ligament, 

 a thin and short band of fibres which passes 

 transversely from the ridge separating the two 

 articular surfaces on the head of the rib, to 

 the inter-vertebral substance, and divides the 

 articulation into two parts, each lined by a 

 separate synovial membrane. This ligament 

 does not exist in the articulation of the 1st, 

 1 1th, and 12th ribs, and in consequence there 

 is in them but one synovial membrane. 



2ndly. With the transverse processes of two 

 vertebra. The rib at its tubercle forms a 

 joint, lined by synovial membrane, with one 

 transverse process ; and to another (being 

 separated from it by a considerable interval), 

 it is connected by ligamentous structure of 

 some length. The costo-transverse ligaments 

 connect the tubercle and neck of the rib with 

 the transverse processes of the vertebrae ; they 

 are named from their position, posterior, mid- 

 dle, and anterior. 



a. The posterior costo-transverse ligament 

 (Jig. transversum externum costarum, Weitbr.) 

 consists of a very short, thick fasciculus of 

 fibres, which passes from the posterior surface 

 of the summit of the transverse process, to 

 the rough, inarticular part of the tubercle of 

 the rib. Those of the superior rib ascend, 

 those of the inferior rib somewhat descend. 



b. The middle, or interosseous costo-trans- 

 verse ligament consists of a series of very 

 short parallel fibres, which unite the neck of 

 the rib to the anterio surface of the con- 

 tiguous transverse process. These fibres are 

 best seen by removing horizontally a portion 

 of the rib and transverse process, and ifor- 

 cibly drawing one from the other. 



c. The anterior, or long costo-transverse 

 ligament (Jig. transversum internum sen cer- 

 vicis costce internum, Weitbr.), is usually di- 

 vided into two fasciculi of fibres nearly op- 

 posite to one another, and on the same plane. 

 They pass from the neck of the rib obliquely 

 upwards and outwards to the lower, margin 

 of the transverse process next above it. 



Characters peculiar to certain costo- vertebral 

 articulations. The articulations of the 1 st, 

 llth, and 12th ribs alone present peculiarities. 



a. Costo-vertebral articulation of the 1st rib. 

 The rounded head of the 1st rib is received 

 into a cavity on the side of the body of the 

 1st dorsal vertebra, the articulation is therefore 

 a species of enarthrosis ; there is neither a 

 costo-vertebral interosseous ligament, nor a 

 superior costo-transverse ligament ; the syno- 

 vial membrane is much looser than in the cor- 

 responding articulations of other ribs. 



b. Costo-verlebral articulation of the 1 \th 

 and \2th ribs. These present the same cha- 

 racters as the preceding, in this respect, that 

 the anterior cavity for the head of the bone is 

 situated upon a single vertebra. The head of 

 the rib, however, is flattened, or very slightly 

 convex. There is no interosseous costo- 

 vertebral ligament. The superior costo-trans- 

 verse ligament is much broader and stronger 

 than in the other articulations. As the llth 

 and 12th ribs have no tubercles, and the 

 transverse processes of the corresponding 

 vertebras are but little developed, it follows 

 that there is no costo-transverse articulation : 

 but yet there is a costo-transverse interos- 

 seous ligament. All these ligaments are much 

 more loose than in the other articulations. 



Srdly. With the sternum (Chondro-sternal 

 articulation). The costo-sternal articulation 

 is between the angular extremities of the car- 

 tilages of the ribs and the corresponding 

 fosste in the margins of the sternum ; these ar- 

 ticulations are covered and supported by two 

 sets of ligaments. 1st, by an anterior set of 

 ligamentous fibres, thin, scattered, and radi- 

 ated (ligamenta radiatim disjecta Weitbr.), 

 passing from the extremity of the cartilage 

 to the anterior surface of the sternum, 

 where they interlace with those of the op- 

 posite side, and are blended with the apo- 

 neurosis of the pectoralis major muscle. 

 2ndly, by a posterior set of fibres similarly 

 disposed, but not so thick or numerous, con- 

 necting the thoracic surfaces of the same 

 parts ; together with some ligamentous fibres 

 placed above, and others below the joint. 



A synovial membrane is interposed be-, 

 tween the ends of each true rib, and thti 

 sternum. These membranes can be demon- 

 strated by slicing off a little of the anterior 

 surface of the sternum and cartilages. Cruveil- 

 hier doubts the existence of such synovial 

 membranes ; we are inclined to differ from him 

 in this respect. 



Characters peculiar to chondro- or costo- 

 sternal articulations. The 1st, 2nd, 6th, and 

 7th chondro-sternal articulations present the 

 following peculiarities : 



1st, The cartilage of the 1st rib is some- 



