THE STERNUM. 99 



sents for examination an anterior and posterior surface; 

 superior, inferior, and lateral borders. The anterior sur- 

 face, convex from side to side, gives attachment to the 

 fibres of the pectoralis major and sterno-mastoid muscles. 

 The posterior surface, flat, gives origin to the sterno- 

 thyroid and sterno-hyoid muscles. The superior border 

 is thick, notched and rounded, and presents, at the 

 angles of the superior and lateral borders, the concave 

 articular surfaces for the clavicles. The lateral border 

 presents, above, the articular facet for the first costal car- 

 tilage ; this border then passes downward and inward, 

 presenting at the angles with the inferior border a half- 

 facet for the articulation with the second costal cartilage. 

 The inferior border is rough and covered with cartilage, 

 by which it articulates with the second piece of the 

 sternum, the gladiolus. The gladiolus, four to five 

 inches long, one and one-half inches broad, one-third of 

 an inch thick, is a flat plate of bone, presenting anteriorly 

 four transverse ridges, which mark the original division 

 of the bone into five pieces ; the lower ridge is faintly 

 developed. From this surface arise the fibres of the 

 pectoralis major muscle. The posterior surface also pre- 

 sents the transverse ridges, but less marked. It presents 

 a number of foramina for the passage of vessels. The 

 lateral borders present four complete and superior and 

 inferior half-notches. These notches are at the ends 

 of the transverse ridges, and serve for the articulation 

 of the costal cartilages. Between them the bone is 

 concave and rounded. The superior border articulates 

 with the manubrium, and presents at each angle the 

 half-notch. The inferior border articulates with the ensi- 

 form appendix, and presents at each angle also a half- 

 facet. 



The ensiform appendix, largely cartilaginous in char- 



