STEKNO-COSTAL JOINTS. 315 



extensions to the adjoining rib and its costo-transverse articular capsule. Others 

 proceed almost vertically, upwards to the adjoining transverse process, while those 

 which ascend from the upper surface of the tubercle pass obliquely upwards and 

 inwards to reach the postero-inferior aspect of the adjoining transverse process. 

 Some posterior fibres connected with the transverse process at its junction with 

 the lamina are called the posterior costo-transverse ligament. 



Lig. Tuberculi Costae. The ligament of the tubercle of the rib is a band of 

 transverse fibres applied to the postero-lateral aspect of the capsule. By one end 

 these fibres are attached to the tip of the transverse process behind its articular 

 facet, and by the other to the external rough surface of the tubercle of the rib. 



Lig. Colli Costse. The ligament of the neck of the rib (O.T. middle costo- 

 transverse ligament) consists of short fibres which stretch from the posterior aspect 

 of the neck of the rib, backwards and medially, to the anterior aspect of the 

 transverse process, but, in addition, a proportion of the fibres passes to the posterior 

 aspect of the inferior articular process of the upper of the two vertebrae with which 

 the head of the rib articulates. 



The following exceptions to the general plan of rib-articulation indicated above 

 must be noted : 



II. There is no articulation between the eleventh and twelfth ribs and the 

 transverse processes of the corresponding vertebrae. 

 2. The anterior costo-transverse ligament is wanting from the first rib, and is 

 either rudimentary or wanting in the case of the twelfth rib. 

 3. The lig. colli costse is rudimentary in the eleventh and twelfth ribs. 

 The ligamentum lumbocostale extends from the superior surface of the base of the 

 transverse process of the first lumbar vertebra to the inferior surface of the neck of 

 the twelfth rib, as well as to the inferior surface of the transverse process of the 

 twelfth thoracic vertebra. 



ARTICULATIONES COSTOCHONDRALES. 



Each rib possesses an unossified portion, termed its costal cartilage. As age 

 advances, this cartilage may undergo a certain amount of superficial ossification, 

 but it never becomes entirely transformed. The line of demarcation between 

 bone and cartilage is clear and abrupt, and usually the bone forms an oval cup, in 

 which the end of the cartilage is retained by means of the continuity which exists 

 between the periosteum and the perichondrium. There is no articulation in the 

 proper sense between the rib and its cartilage, although a synovial cavity has 

 occasionally been found between the first rib and its cartilage. 



ARTICULATIONES INTERCHONDRALES. 



Interchondral joints are arthrodial diarthroses, and they are found between 

 adjoining margins of certain of the costal cartilages, viz., from the fifth to the eighth 

 or ninth. The cartilages which thus articulate develop flattened, somewhat conical, 

 prolongations of their substance, and thereby the intercostal spaces are interrupted 

 where these flat articular facets abut against each other. Each joint is closed 

 by a surrounding articular capsule, the superficial and thoracic aspects of which are 

 specially strengthened by external and internal interchondral ligaments. These 

 bands extend obliquely between adjacent cartilages. 



A stratum synoviale lines each joint capsule. 



The upper seven pairs of costal cartilages, as a rule, extend to the lateral 

 margins of the sternum to form sterno-costal joints. Of these, the first pair is 

 implanted directly upon the manubrium sterni. The ossific process ends abruptly 

 in connexion with the rib, and also ceases as suddenly in connexion with the 

 sternum, and hence the cartilage does not normally present an articulation at 

 either end. From the second to the seventh pairs of ribs inclusive, the sterno-costal 

 joints are constructed upon the type of arthrodial diarthroses, although, in the case 



ARTICULATIONES STERNOCOSTALES. 



