THOEACIC LIMBS 525 



widened from before backward. It presents an emarginate anterior 

 border, to which is attached the deltoid muscle ; a middle prominence 

 thereon is sometimes termed the deltoid tubercle. The wider arcuate 

 posterior border is occupied by the trapezius muscle. It terminates 

 medially in the large, rough- 

 ened conoid tuberosity for the FIG. 416. 

 conoid part of the coraco- 

 clavicular ligament. The ter- 

 minal lateral border presents 



RIGHT CLAVICLE, UPPER VIEW. 



a flattened OVal lacet, WrilCll I, sternal end; 2, portion which joins the cartilage of the 



P -IT .11 first rib ' 3> line of attacnm ent of the pectoral muscle on 



laces OUtWarCl, ClOWnWaru, and anterior surface; 4, superior surface of the acromial end; 



n -i -I .. -i .,-1 5, its articular surface ; 6, anterior border, giving attachment 



forward, and artlCUlateS Wltll to the deltoid muscle; 7, posterior border, giving attach- 



,-i - n ,i ment to the trapezius muscle; 8, superior border, position 



the oval facet on the inner of origin of the ste rno-mastoid muscle. 

 margin of the acromion of the 



scapula. The superior surface is flat, roughened in front for the 

 attachment of the deltoid, and roughened behind for the attachment 

 of the trapezius ; laterally a small portion is subcutaneous. The infe- 

 rior surface is flat and crossed by an oblique line which passes from 

 the conoid tubercle outward and forward to the anterior border and 

 affords attachment to the trapezoid division of the corg,co-clavicular 

 ligament. 



The part forming the inner two-thirds of the clavicle is prismatic 

 or quadrilateral. At the outer end, where it is continuous with the 

 outer part, it is narrower and prismatic ; at the inner end it is swollen, 

 especially behind (dorsally), and is almost cylindrical. It is by some 

 authors described as having two surfaces, by others as having three 

 surfaces, while others again distinguish four surfaces. Three surfaces, 

 anterior, posterior, and inferior, are always distinct, separated by supe- 

 rior, anterior, and posterior borders. The sinuous superior border is 

 the continuation inward of the anterior border of the outer part; it 

 passes somewhat backward at the inner end, where it is elevated for 

 the pectoralis major muscle. The posterior border begins laterally at 

 the conoid tubercle and ends medially in the roughened triangular 

 space on the posterior inferior aspect called the rhomboid impression, 

 because to it is attached the costo-clavicular or rhomboid ligament. 

 The anterior border is also the continuation inward of the anterior 

 border of the flattened outer part. It is on the inferior aspect of the 

 bone. Between the anterior and posterior borders is the inferior 



