12 



VEETEBEAL COLUMIS'. 



processes are smaller than the superior, flat, nearly circular, looking 

 downwards and slightly inwards. 



The posterior arch presents in the middle line a rough elevation, the 

 rudiment of a spinous process. The rest of the arch is thick and 

 round, but at its junction with the lateral masses, it is hollowed out 

 superiorly, so as to form a smooth transverse groove, in ^vhicll lie the 

 vertebral artery and first s[)inal (sub-occipital) nerve. It is sometimes 

 converted into a foramen by a small arch of bone, and corresponds to 

 the notches of the other vertebra. 



The tramverxe. jjvocesses are larger and project further outwards than 

 tliose of the subjacent vertebrae. They are flattened from above down- 

 wards, and have the foramen for the vertebral artery at their roots. 

 Their extremities are not bifid, but broad and rough. 



The Second Vertebra. — Axis (vert, dentata) forms a pivot on which 

 the head with the first vertebra rotates. 



The body is characterised by the presence of a large blunt or tooth- 

 like process called odontoid (proc. dentatus). This consists of an enlarged 



part termed the head, and a lower part 

 '^'^S- '• or ncch. It presents in front a smooth 



surface for articulation with the atlas, and 

 behind a smooth groove to receive the 

 transverse ligament. The lower surface 



Fig. 7.— The Axis Vektebra. (A. T.) 4 



A, seen from above and behind ; B, seen from the 

 right side. 1, tlie body ; 4, tlie vertebral ring 

 or foramen ; 5, the spinous process, bifid and very 

 large ; 6, the transverse process ; 7, the superior 

 articular jjrocess ; 7', the inferior oblique articu- 

 lar ijrocess ; 1* in A, is placed at the side of the 

 odontoid process ; in B, in front of it, marking the 

 smooth surface of articulation with the anterior arch 

 of the atlas. 



of the body resembles that of the suc- 

 ceeding vertebras. Its anterior surface 

 presents a low median vertical ridge, with 

 a depression on each side. 



The superior articular surfaces placed like those of the atlas in front 

 of the notch, lie close to the base of the odontoid process, partly on the 

 body and partly on the arch of the vertebra. These surfaces look 

 upwards and slightly outwards. The inferior articular processes are 

 similar in form and position to those of the succeeding vertebras. 



The spinous process is very large, rough, deeply bifid, and grooved on 

 its inferior surface. The Jamineo are very thick and strong. 



The transverse ]n~ocesses are short, and scarcely grooved and bifurcated. 

 The foramen for the vertebral artery is inclined obliquely downwards 

 and inwards. 



Dorsal Vertebras. — These are twelve in number, and support the 

 ribs. 



The body as seen from above is somewhat heart-shaped ; its antero- 

 posterior and transverse diameters are nearly equal. 



It is specially characterised l)y the presence, at the place where it 

 joins the arch, of depressed articular surfaces for the heads of ribs. In 



