ARTICULATIONS OF THE THORAX. 281 



Anterior Articulations of the Ribs. 



The surface of each pit in the side of the sternum is covered 

 by a thin cartilaginous plate, to receive the corresponding car- 

 tilage of the rib, and the articulation presents an anterior and 

 a posterior ligament, also a synovial capsule. 



The anterior ligament arises from the extremity of the car- 

 tilage, and, going over the front of the sternum, radiates very 

 considerably in every direction. Some of its fibres are con- 

 tinuous with the corresponding fibres of the opposite side; 

 others are lost in the periosteum and in the tendinous origin of 

 the great pectoral muscle; others join the fibres of the ligament 

 above, and of that below. The more superficial the fibres are, 

 the longer they become; but the more deeply seated pass only 

 from the margin of the cartilage to the margin of the cavity in 

 the sternum. The thick ligamentous covering found on the 

 front of the sternum, may be considered as only the continua- 

 tion of these anterior ligaments. The fibres from the two lower 

 articulations on the opposite side, form, by their junction, a 

 striking triangular ligamentous plane, just on the lower end of 

 the second bone of the sternum. Besides which, there are se- 

 veral strong ligamentous fasciculi running in a great variety of 

 directions. 



The posterior ligament has a similar arrangement with the 

 anterior, in the radiation of its fibres into the contiguous, liga- 

 ments, and in their origin from the costal cartilage. Altogether 

 they form, on the posterior face of the sternum, a strong, smooth 

 covering, the fibres of which do not run in fasciculi, but present 

 a uniform polished membrane, and are closely interwoven with 

 each other. Some of these fibres are longitudinal, and, of 

 course, cannot be referred to the posterior ligaments, but are 

 independent of them. 



The synovial membrane, though its existence is admitted, is 

 not in a very distinct state. It scarcely gives a polish to the 

 articular surfaces, and has so little looseness in its reflection 

 from the one to the other, as to indicate clearly that but an in- 



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