8 HANDBOOK OF ANATOMY 



and outwards, overhangs the glenoid surface ; it is very much 

 roughened for the attachment of muscles and ligaments. 



The anterior, or ventral, surface of the bone is concave, and 

 has several rough lines on it, caused by the attachment of the 

 subscapular muscle. The axillary border on this surface is full 

 and rounded, the vertebral border being roughened. Both 

 borders give attachment to muscles. 



The posterior dorsal surface is divided into an upper smaller 

 fossa and a lower larger fossa by the spine, which runs from 

 the vertebral border outwards and upwards to the glenoid 

 cavity. Both fossse give attachment to muscles. The spine 

 is separated from the edge of the glenoid cavity by the great 

 scapular notch ; the posterior border is subcutaneous, and is 

 lipped for the attachment of muscles; at the great scapular 

 notch it is flattened to form the acromion process, which passes 

 forwards and outwards to overhang the joint, and gives attach- 

 ment to muscles and ligaments. 



The scapula articulates by means of the glenoid cavity with 

 the head of the humerus, and by the acromion process with the 

 acromial end of the clavicle. 



Ossification. At birth the coracoid and acromion processes, 

 the glenoid cavity, and vertebral border are still cartilaginous. 

 Secondary centres appear in these from birth up to puberty, 

 and the bone is complete about the twentieth year. 



The Humerus is a long bone with a shaft and two extremities ; 

 it is the bone of the upper arm. It has a rounded head forming 

 about one-third of a sphere, which is bounded by the anatomical 

 neck, a shallow depression all round the head, much less marked 

 inferiorly. On the outer side of the head is the great tuberosity, 

 which becomes continuous with the shaft, and has facets for 

 the attachment of muscles. On the anterior surface of the 

 upper end is the lesser tuberosity, which also becomes con- 

 tinuous with the shaft. Between the two tuberosities lies the 

 bicipital groove, which gives attachment to the adductor 

 muscles. Below the head and tuberosities the bone decreases 

 in size, and this is called the " surgical neck," as it is the part 

 most easily fractured. 



The shaft is cylindrical above, but gets flatter lower down. 



