136 



PRINCIPLES OF ANIMAL BIOLOGY 



To it is attached the hyoid apparatus which is a bony or cartilaginous 

 support for the base of the tongue. 



The vertebral column is a jointed structure composed of a number 

 (different in different species) of vertebrae placed end to end. Together 

 they form a tube enclosing the spinal cord, and their outer surfaces form 



VERTfBRAL OOLUMN. 



Lumbar 



SacToJ. 



Fig. 103. — Axial skeleton of the cat. (From Jayne's Mammalian Anatojny.) 



attachments for ligaments and muscles. The vertebral column is 

 structurally differentiated into five regions, cervical, thoracic, lumbar, 

 sacral, and caudal regions (Fig. 103). The plan of a vertebra is shown 

 in Fig. 104. It is composed of a heavy ventral portion, the centrum, from 

 which arises a bony arch, the neural arch. The latter encloses the neural 



na 



FiQ. 104. — Diagram of a typical ver- 

 tebra viewed from in front or from behind, 

 c, centrum; na, neural arch; nc, neural 

 canal; ns, neural spine; tp, transverse 

 process; z, zygapophysis. 



Fig. 1C5. — Diagram of two typical vertebrae 

 A'iewed from the side, with anterior end at the 

 left, az, anterior zygapophysis; c, centrum; /, 

 intervertebral foramen through which nerves 

 and bloodvessels pass; ic, intervertebral carti- 

 lage; na, neural arch; ns, neural spine; pz, pos- 

 terior zygapophysis; tp, transverse process. 



canal which is occupied by the spinal cord. From the sides of the arch 

 two transverse processes project, and from the apex of the arch arises the 

 neural spine. One pair of articular processes or zygapophyses project 

 anteriorly and another posteriorly from the sides of the arch. The rela- 

 tions of the anterior and posterior zygapophyses and the articular faces 

 of the centra of adjoining vertebrae are made clear in Fig. 105. 



