CLAVICLE SCAPULA. 103 



Articulations. Each rib articulates with two vertebrae, and one costal 

 cartilage, with the exception of the first, tenth, eleventh, and twelfth, 

 which articulate each with a single vertebra only. 



Attachment of Muscles. To the ribs and their cartilages are attached 

 twenty-two pairs, and one single muscle. To the cartilages, the subcla- 

 vius, sterno-thyroid, pectoralis major, internal oblique, rectus, transversa- 

 lis, diaphragm, triangularis sterni, internal and external intercostals. To 

 the ribs, the intercostal muscles, scalenus anticus, scalenus posticus, pec- 

 toralis minor, serratus magnus, obliquus externus, obliquus internus, latis- 

 simus dorsi, quadratus lumborum, serratus posticus superior, serratus pos- 

 ticus inferior, sacro-lumbalis, longissimus dorsi, cervicalis ascendens, leva- 

 tores costarum, transversalis, and diaphragm. 



CLAVICLE. The clavicle is a long bone shaped like the italic letter f t 

 and extended across the upper part of the side of the chest from the upper 

 piece of the sternum to the point of the shoulder, where it articulates with 

 the scapula. In position it is very slightly oblique, the sternal end being 

 somewhat lower and more anterior than the scapular, and the curves are 

 so disposed that at the sternal end the convexity, and at the scapular the 

 concavity, is directed forwards. The sternal half of the bone is rounded 

 or irregularly quadrilateral, and terminates in a broad articular surface. 

 The scapular half is flattened from above downwards, and broad at its 

 extremity, the articular surface occupying only part of its extent. The 

 upper surface is smooth and convex, and partly subcutaneous ; while the 

 under surface is rough and depressed, for the insertion of the subclavius 

 muscle. At the sternal extremity of the under surface is a very rough 

 prominence, which gives attachment to the rhomboid ligament ; and at 

 the other extremity a rough tubercle and ridge, for the coraco- clavicular 

 ligament. The opening for the nutritious vessels is seen upon the under 

 surface of the bone. 



Development. By two centres; one for the shaft and one for the sternal 

 extremity ; the former appearing before any other bone of the skeleton, 

 the latter between fifteen and eighteen. 



Articulations. With the sternum and scapula. 



Attachment of Muscles. To six ; the sterno-mastoid, trapezius, pecto- 

 ralis major, deltoid, subclavius, and sterno-hyoid. 



SCAPULA. The scapula is a flat triangular bone, situated upon the pos- 

 terior aspect and side of the thorax occupying the space from the second 

 to the seventh rib. It is divisible into an anterior and posterior surface, 

 superior, inferior, and posterior border, anterior, superior, and inferior 

 angle, and processes. 



The anterior surface or subscapular fossa, is concave and irregular, and 

 marked by several oblique ridges which have a direction upwards and 

 outwards. The whole concavity is occupied by the subscapularis muscle, 

 with the exception of a small triangular portion near the superior angle 

 The posterior surface or dorsum is convex, and unequally divided into 

 two portions by the spine ; that portion above the spine is the supra-spin 

 ous fossa ; and that below, the infra-spinous fossa. 



The superior border is the shortest of the three : it is thin and concave, 

 and terminated at one extremity by the superior angle, and at the other by 

 the coracoid process. At its inner termination, and formed partly by the 



