VERTEBRAL COLUMN 



163 



Fig. 169. — Axis of Pig; Lateral View. 

 1, Dens; 2, 2', anterior and posterior articular 

 processes; 3, posterior end of body; 4, transverse proc- 

 ess: 5, foramen transversarium ; 6, arch; 7, spinous 

 process. Arrow indicates intervertebral foramen. 



Fig. 170. — Axis of Pig; Anterior View. 

 1, Dens; 2, 2', anterior and posterior articular 

 processes; 3, foramen transversarium; 4, arch; S. spi- 

 nous process. 



posterior border of the wing to tlie fossa under the latter, and is not visible dorsally; 

 it is sometimes very small or absent. The 

 sides of the vertebral foramen bear two lat- 

 eral projections which partially divide it 

 into a ventral narrow part, which receives 

 the dens, and a dorsal larger part for the 

 spinal cord. In the fresh state the division 

 is completed by the transverse ligament, 

 which is attached to the projections. 



The axis has a large spinous process, 

 which is directed upward and backward. 

 The dens is a thick cylindrical rod. The 

 transverse process is very small and the 

 foramen transversarium is often incom- 

 plete. 



The thoracic vertebrae are commonly 

 fourteen or fifteen in number. Their 

 bodies are relatively long, constricted in 

 the middle, and without ventral spines. 

 Their extremities are elliptical, depressed 

 in the middle, and prominent at the peri- 

 phery. The arch is perforated by a fora- 

 men on each side and in most of the series 

 there is also a foramen in the posterior 

 part of the root of the transverse process 

 which communicates with the former or 

 with the posterior intervertebral foramen. 

 Sometimes there is a foramen in the an- 

 terior part of the process also. There are 

 mammillary processes except on the first 

 two; in the posterior five or six vertebrae 

 they project from the anterior articular 

 processes. The facet for the tubercle of the 

 rib is absent or fused with that for the 

 head in the last five or six. The last trans- 



FiG. 171.- 



Second and Third Thoracic Vertebr.e 

 OF Pig; Lateral View. 

 Numbers around bones: 1, 1', Anterior and poster- 

 ior ends of bodies; 2, ca^vitieaforheadsof ribs;3, 3', artic- 

 ular process; 4, facet for head of rib; 5, spinous process. 

 Numbers on bones: 1, 1', Foramina of arches; 2, 2% 

 transverse processes; 3, 3', facets for tubercles of ribs. 



