CBBVICAIj vertebrje. 171 



absence of the neural foramen, the caudal inclination of the dia- 

 pophyses when present, and by the presence in some (2d to 9th) of 

 the so-called chevron bones. 



§ 465. The chemon hones are small ossicles attached to the cephalo-ventral part of the 

 caudal veitebrse and forming an open or closed arch through which passes the caudal con- 

 tinuation of the A. sacra media. 



The ends of the vertebrae may be distinguished very readily by remembering that the 

 arthral surface of the prmzygapophysis (Fig. 53), situated at the cephalic end of the verte- 

 bra, faces either dorsad or dorso-mesad, while that of the postzygapophyHs faces ventrad 

 or ventro-laterad. It follows from this that the postzygapophyses overlie the prsezyga- 

 pophyses like the tiles on a roof. Especially in the thoracic and lumbar regions, the Inoi- 

 sura vertebralis or intervertebral notch is much deeper on the caudal than on the cephalic 

 side. The above characters apply also to man. 



§ 466. Demonstration. — All of the general as well as special 

 points relating to the vertebral column may be demonstrated on a 

 flexible natural skeleton (§ 252) and one entirely divested of its soft 

 parts. The relation of the myelon and other soft parts must of 

 course be demonstrated on a fresh or alcoholic specimen. 



§ 467. Preparation — (Pig. 52). — The cleaning (§ 253), was carried sufficiently far to 

 divest this part of the vertebral column of all its soft parts except the intervertebral fibro- 

 cartilages. 



§ 468. Arthron capitelli — Capitellar articulation. — This is the diarthrodial arthral cav- 

 ity formed in two adjacent thoracic vertebrae for the reception of the capitellum or head of 

 the rib (Pig. 50). The part of the articulation in each vertebra is called a demifaeet. The 

 12th and 13th vertebrae have each a complete capitellar arthral surface. The caudal part 

 of the last cervical vertebra supports part of the capitellum of the first rib ; Plower, A, 23. 



§ 469. Arthron tuberculi. — This is the diarthrodial facet on the diapophysis for 

 articulation with the rib corresponding in number to the vertebra from which the dia- 

 pophysis arises (Fig. 50, 53). It is not present in the last two thoracic vertebrae. 



§ 470. Atlas. — The atlas is the first cervical vertebra, and thus the first of the entire 

 series. It articulates diarthrodially with the occipital condyles (Pig. 57). The broad lat- 

 eral masses are the diapnpliyaes or transverse processes, and are sometimes called " wings 

 of the atlas." 



§ 471. Axis. — This is the second of the cervical vertebrse. It articulates diarthrodi- 

 ally with the atlas, but with the third vertebra by the interposition of fibro-cartilage, that 

 is, amphiarthrodially, like the remaining vertebrae, except the sacrum (§ 458). Its neural 

 spine is a long sharp ridge (Pig. 30). 



Cerv. — ^Vertebrae cervicales, cervical vertebrse 1-7. 



§ 472. Fibro-cartilago intervertebralis, az. — Intervertebral fibro-cartilage.— Between 

 each of the centra, except the first and second and the parts of the sacrum, is this very 

 dense, tough and elastic fibrous material. "The elasticity provides for the vertebrae 

 always returning to their normal relation to each other and the column generally when 

 they have been disturbed therefrom by muscular action. "—Plower, A, 13. 



§ 473. Foramen vert., Fm. vertebrarteriale.— This is the canal through the bases 



