DORSAL VERTEBRAE. 45 



gradually becomes ossified at its circumference, but remains cartilaginous in its 

 centre until advanced age. 1 Finally, as Humphry has demonstrated, the apex of 

 the odontoid process has a separate nucleus, which appears in the second year and 

 joins about the twelfth year. In addition to these there is a secondary centre for 

 a thin epiphysial plate on the under surface of the body of the bone. 



The Seventh Cervical. The anterior or costal part of the transverse process 

 of the seventh cervical is developed from a separate osseous centre at about the 

 sixth month of foetal life, and joins the body and posterior division of the trans- 

 verse process between the fifth and sixth years. Sometimes this process continues 

 as a separate piece, and, becoming lengthened outward, constitutes what is known 

 as a cervical rib. This separate ossific centre for the costal process has also been 

 found in the fourth, fifth, and sixth cervical vertebrae. 



The Lumbar Vertebrae (Fig. 14) have two additional centres (besides those 

 peculiar to the vertebrae generally) for the mammillary tubercles, which project 

 from the back part of the superior articular processes. The transverse process of 

 the first lumbar is sometimes developed as a separate piece, which may remain 

 permanently unconnected with the remaining portion of the bone, thus forming a 

 lumbar rib a peculiarity that is rarely met with. 



Progress of Ossification in the Spine generally. Ossification of the laminae of 

 the vertebrae commences in the cervical region of the spine, and proceeds gradually 

 downward. Ossification of the bodies, on the other hand, commences a little 

 below the centre of the spinal column (about the ninth or tenth dorsal vertebra), 

 and extends both upward and downward. Although, however, the ossific nuclei 

 make their first appearance in the lower dorsal vertebrae, the lumbar and first 

 sacral are those in which these nuclei are largest at birth. 



Attachment of Muscles. To the Atlas are attached nine pairs : the Longus 

 colli, Rectus capitis anticus minor, Rectus lateralis, Obliquus capitis superior and 

 inferior, Splenius colli, Levator anguli scapulae, First Intertransverse, and Rectus 

 capitis posticus minor. 



To the Axis are attached eleven pairs : the Longus colli, Levator anguli 

 scapulas, Splenius colli, Scalenus medius, Transversalis colli, Intertransversales, 

 Obliquus capitis inferior, Rectus capitis posticus major, Semispinalis colli, Mul- 

 tifidus spinge, Interspinales. 



To the remaining vertebrae, generally, are attached thirty-five pairs and a sin- 

 gle muscle: anteriorly, the Rectus capitis anticus major, Longus colli, Scalenus 

 anticus medius and posticus, Psoas magnus and parvus, Quadratus lumbo- 

 rum, Diaphragm, Obliquus abdominis internus, and Transversalis abdominis 

 posteriorly, the Trapezius, Latissimus dorsi, Levator anguli scapulas, Rhomboideus 

 major and minor, Serratus posticus superior and inferior, Splenius, Erector spinge, 

 Ilio-costalis, Longissimus dorsi, Spinalis dorsi, Cervicalis ascendens, Transversalis 

 colli, Trachelo-mastoid, Complexus, Biventer cervicis, Semispinalis dorsi and colli, 

 Multifidus spinae, Rotatores spinge, Interspinales, Supraspinales, Intertransversales, 

 Levatores costarum. 



Sacral and Coccygeal Vertebrae. 



The Sacral and Coccygeal Vertebrae consist, at an early period of life, of nine 

 separate pieces, which are united in the adult so as to form two bones, five enter- 

 ing into the formation of the sacrum, four into that of the coccyx. Occasionally, 

 the coccyx consists of five bones. 2 



The Sacrum (sacer, sacred) is a large, triangular bone (Fig. 15), situated at the 

 lower part of the vertebral column, and at the upper and back part of the pelvic 

 cavity, where it is inserted like a wedge between the two innominate bones : its 

 upper part or base articulating with the last lumbar vertebrae, its apex with the 

 coccyx. The sacrum is curved upon itself, and placed very obliquely, its upper 



1 See Cunningham, Jonrn. Anat., vol. xx. p. 238. 



2 Sir George Humphry describes this as the usual composition of the coccyx. On the Skeleton, 

 i). 456. 



