OSTEOLOGY. 43 



Muscular attachments are twenty scalenus anticus, medius, 

 and posticus, pectoralis minor, intercostals, serratus magnus, ob- 

 liquus externus, transversalis, quadratus lumborum, diaphragm, 

 latissimus dorsi, serratus posticus, superior and inferior; sacro- 

 lumbalis, musculus accessorius ad ilio-costaleni, levatores costa- 

 rum, longissimus dorsi, cervicalis ascendens, and infracostales. 



They are developed from thirty-four ossific centres, each 

 rib having one centre each for its head, shaft, and tubercle, 

 except the eleventh and twelfth, which have but two centres, not 

 having any tubercles. 



VERTEBRA. 



The SPINE, or vertebral column, is a flexible column com- 

 posed of twenty-six bones (thirty-three vertebra), as follows: 



FIG. 18. 



1, body; 2, demi-facet for rib; 3, superior articular processes; 

 5, intervertebral notch; 6, spinous process; 7, facet for tubercle on 

 transverse process; 9, inferior articular processes. 



seven cervical, twelve dorsal, five lumbar, sacrum, and coccyx. 

 Each vertebra consists of a body, and an arch composed of two 

 pedicles and two laminae, supporting seven processes one spi- 

 nous, two transverse, and four articular. 



The body (centrum), the large, solid, anterior portion, is 

 generally half-cylindrical, concave behind, convex in front and 

 sides. Its upper and lower surfaces are broad and rough, for 

 attachment of interarticular cartilages. Its posterior surface has 

 large foramen for exit of veins. 



The pedicles project backward (except the cervical, which 

 project obliquely outward), and present four intervertelnil 

 notches, two each, above and below. These, when articulated, 

 form interarlicuhir foramina for exit of spinal nerves and pas- 

 sage of blood-vessels. 



