THE RIBS 



129 



with ouly one articular facet. The neck, longer than that of most of the ribs, is slender and 

 rounded. The tubercle is large and prominent. The shaft lies for its whole extent nearly in 

 one plane, has no angle, and is curved in one direction only, i. e., around a vertical axis. The su- 

 perior surface presents two shallow grooves, separated near the inner border by a rough surface 

 (scalene tubercle or tubercle of Lisfranc) for the scalenus anterior muscle. The groove in 

 front of this surface is for the subclavian vein, and the groove behind it is for the subclavian 

 artery and a nerve trunk passing to the brachial plexus. Between the groove for the arterj' and 

 the tubercle is a rough surface for the insertion of the scalenus medius, and between the groove 

 and the outer margin is an area for the origin of the serratus anterior {magniis). The inferior 

 surface is uniformly flat and lacks a subcostal gi'oove. By the lateral portion, which is rough, 

 it gives attachment to the internal intercostal muscle; the remainder of the inferior surface is in 

 relation to pleura and lung. The lateral border is thick and rounded, and gives attachment 

 to the external intercostal muscle, whilst the medial border, thin, sharp, and concave, receives 

 the attachment of the fascia (Sibson's) covering the dome of the pleura. The anterior extrem- 

 ity is thick and broad, and its upper margin, as well as the cartilage to which it is joined, afford 

 attachment to the costo-clavicular ligament and the subclavius muscle. The costal cartilage 

 of this rib is directly united to the manubrium sterni, and occasionally the cartilage and the 

 adjoining part of the anterior extremity of the rib are replaced by fibrous tissue. 



Fig. 155.— First and Second Rebs. (Viewed from above.) 



Tubercle 



Levator costae and _^ 

 ilio-costalis dorsi'^SS^:^ 



Scalenus medius 



Groove for subclavian 

 artery 



Scalenus anterior 



Groove for subclavian 

 vein 



Shaft 



Levator costse 

 Ilio-costalis dorsi 



(insertion) 

 Ilio-costalis cervicis 



(origin) 

 Serratus posterior 



superior 



(insertion) 

 Scalenus posterior 



Third digitation of 

 serratus anterior 



External intercostals 



The rib derives its nutrition mainly from the superior intercostal branch of the subclavian 

 artery. 



The second rib is much longer than the first, and although like it in being strongly curved 

 round a vertical axis, in its form and general characters there is a closer resemblance to the 

 ribs lower down in the series. The head is round and presents two facets, the costal groove is 

 present, though faintly marked, and an angle is situated near the tubercle. The specially dis- 

 tinguishing feature of the rib, however, is a well-marked tuberosity on its outer surface some- 

 what near the middle, for the origin of a part of the first digitation, and the whole of the second 

 digitation of the serratus anterior {magnus). Between the tuberosity and the tubercle the outer 

 surface is smooth and rounded and gives attachment to the scalenus posterior, the serratus 

 posterior superior, the ilio-costalis cervicis {cervicalis ascendens), and the ilio-costalis dorsi (acces- 

 sorius) . The internal surface is smooth and in relation to the pleura. The borders give attach- 

 ment to the intercostal muscles, the upper, to those of the first space, the lower, to those of the 

 second. The shaft of the second rib is not twisted on its own axis, so that both ends can Ue flat 

 on the table. The second rib receives vessels from the superior intercostal branch of the 

 subclavian artery and the first aortic intercostal. 



The tenth rib is distinguished by a single facet on the head for articulation with the body 

 of the tenth thoracic vertebra. Occasionally there are two facets, in which case the rib articu- 

 lates also with the ninth thoracic vertebra. The tenth rib, like the ribs immediately above, is 

 long, curved, presents a deep costal groove, a well-marked tuberosity and an angle. It may 



