THE KIBS. 



Ill 



Facets on head 



Neck 



Nori -articular 

 part of tubercle 



Articular part of tubercle 

 for transverse process of 

 vertebra 



Angle 



external and internal intercostal muscles respectively. On the floor of the groove 



may also be seen the openings of the canals for the transmission of the nutrient 



vessels, which are directed towards the vertebral end of the rib. 



The anterior or sternal extremity of the body, often slightly enlarged, displays 



an elongated oval pit into which the costal cartilage is sunk. 



Peculiar Ribs. The first, second, tenth, eleventh, and twelfth ribs all display 



characters by which they can be readily recognised. 

 The first rib can be easily 



distinguished from the others 



by its size, curvature, and 



flattened form, as well as by 



the great proportionate width 



of its body. The head, 



which is of small size, has a 



single oval or circular facet, 



which is directed medially 



and slightly backwards for 



articulation with the side of 



the body of the first thoracic 



vertebra. The neck is flat- FIG. 124. FIFTH RIGHT RIB AS SEEN FROM BEHIND. 



tened from above downwards, 



and is slightly down-turned towards the end which supports the head. Its anterior 



border is rounded and smooth; its posterior edge rough for the attachment of 



ligaments. At the point where the neck joins the body posteriorly, a prominent 



tubercle curves upwards and backwards. The inner and lower surface of this 



process has a small circular facet which 

 rests on a corresponding articular sur- 

 face on the transverse process of the 

 first thoracic vertebra. The angle coin- 

 cides with the tubercle, and thus assists 

 in emphasising its prominence. The 

 surfaces of the body of the rib are 

 directed upwards and downwards, its 

 borders inwards and outwards. If the 

 finger is run along the thin inner 

 border, a distinct spine or tubercle can 

 be readily felt about an inch or an inch 

 and a quarter from its anterior ex- 

 tremity. This is the tuberculum scaleni 

 (scalene tubercle of Lisfranc), which also 

 forms an elevation on the upper sur- 

 face of the shaft and affords an attach- 

 ment for the scalenus anterior muscle. 

 There is a shallow, oblique groove 

 crossing the superior surface of the 

 shaft in front of this, for the lodgment 

 of the subclavian vein ; whilst behind 

 the tubercle there is another groove, 

 usually better marked and passing 

 obliquely forwards, for the subclavian 

 artery (sulcus subclavise). In this 

 groove, behind and below the artery, is 

 lodged that part of the first thoracic 

 nerve which contributes to the forma- 

 tion of the brachial plexus. According 



to Wood Jones the development of the groove depends upon the size of the nerve 



passing over it. The space on the upper surface of the rib between this latter 



groove and the tubercle posteriorly is somewhat rough, and affords attachment to 



ithe fibres of the scalenus medius muscle. In manyjspecirnens these features are 



FIG. 125. FIRST AND SECOND RIGHT RIBS AS SEEN 

 FROM ABOVE. 



