OSTEOLOGY. 41 



ANTERIOR REGION presents three pairs : 



Supraorbital foramen, or notch, transmits supraorbital ar- 

 tery, vein, and nerve; 



Infraorbital foramen transmits infraorbital artery and 

 nerve, and 



Mental foramen transmits mental nerve and artery. 



BONES OF THE TRUNK. 



THE STERNUM, or breast-bone, is a long, narrow, sword-like 

 bone occupying the anterior part of the thorax and consisting 

 of three portions: manubrium (handle), gladiolus (blade), 

 xyphoid or ensiform appendix (point). Its anterior surface is 

 irregularly flat, posterior surface slightly concave. 



Manubrium is thick and triangular, and- presents above 

 the interclavicular notch, on either side of which are facets for 

 articulation of clavicles. Laterally it presents an articular facet 

 for the cartilage of the first rib and a half of one for part of 

 second costal cartilage. 



Gladiolus is the longest, narrowest portion, and presents 

 about its centre, between the third and fourth segments, the 

 sternal foramen, and laterally facets for half of the second and 

 for the third, fourth, fifth, and sixth costal cartilages. 



Ensiform appendix is cartilaginous in youth and varies 

 much in size and shape. 



It articulates with the clavicles and seven costal cartilages 

 on side. 



Its ossific centres are six one each for the manubrium and 

 appendix and four for the gladiolus, or body. 



Its muscular attachments are ten sterno-mastoid, sterno- 

 hyoid, sterno-thyroid, pectoralis major, triangularis sterni, ob- 

 liquus externus and internus, transversalis, rectus, and dia- 

 phragm. 



THE RIBS, twelve on each side, form a series of narrow elas- 

 tic arches on each side of the thorax, constituting the chief part 

 of the thorax. They are divided into seven vertebro-sternal, true 

 or sternal, each of which join the sternum by a separate costal 

 cartilage; three vertebro-chondral, or false, the cartilages of 

 which join each other and with the seventh before uniting with 

 the sternum, and two vertebral, free or floating, which have 

 no sternal attachment. 



Each rib consists of a head, neck, tubercle, and body. 



The head presents facet (except the first, tenth, eleventh, 

 and twelfth) for articulation with the bodies of the contiguous 



