14 ANATOMY. 



preceding vertebra, and the latter with the anterior processes of 

 the succeeding. 



The body and arch develop from different centers of ossifi- 

 cation. 



Cervical vertebrae. — There are seven cervical vertebrae, all 

 agreeing in certain general characters. The body is long, thick 

 and has an inferior spine projecting downward from its under 

 surface. The superior spinous processes are long from before to 

 behind, and together form a long rough line. 



The transverse processes are also long from before to behind. 

 In these characteristics the cervical vertebra; differ radically from 

 the others. 



Special cervical vertebrae. — There are certain cervical ver- 

 tebrae which have marked individual peculiarities. The Atlas, 

 immediately supporting the head, has a small thin body with no 

 head, but instead., two surfaces for articulating with the occipital 

 bone. 



The axis is long, and has, in place of the head, a peculiar pro- 

 jection known as "odontoid process." This process is shaped 

 somewhat like a tooth. Hence the name. The spinous process is 

 long from front to rear. 



The seventh cervical vertebra has a long' spinous process, 

 somewhat resemblng those of dorsal vertebrae. It also presents 

 a small articular surface for articulation with the head of the first 

 rib. 



Dorsal vertebrae. — Eighteen in number. These also have cer- 

 tain general characteristics. The body is short. There are four 

 articular cavities, two in front and two behind for the heads of 

 the ribs. Spinous processes are long and flat from side to side. 

 Transverse processes short and small. None of the dorsal ver- 

 tebrae differ very markedly from this general type. 



Lumbar vertebrae. — In general the bod)- is longer and widefr 

 than the doisal. The spinous processes are also shorter. The 

 transverse processes are also long, flat and thin. 



Sacrum. — This consists of five pieces united in the adult. It 

 articulates with the last lumbar vertebra in front, with the first 

 coccygeal vertebra behind and with the pelvis on each side. This 

 portion of the spinal column is triangular with the base forward. 



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