_a_, Wing; _b_, dorsal arch and tubercle; _c_, ventral tubercle; _d_, intervertebral foramen; _e_, foramen transversarium; _f_, articular surface for axis. (Ellenberger-Baum, Anat. d. Hundes.) ] [Illustration: FIG. 117.—AXIS OF DOG, LEFT LATERAL VIEW. _a_, Odontoid process; _b_, articular surface for atlas; _c_, transverse process; _d_; foramen transversarium; _d′_, posterior opening of _d_; _e_, spine; _f_, posterior articular process. (Ellenberger-Baum, Anat. d. Hundes.) ] The =coccygeal vertebræ= are fully developed in the anterior part of the region. The arch is complete in the first six usually. The first three or four have well developed articular processes at each end. Behind this the posterior pair quickly disappears, and the anterior ones become non-articular and gradually reduced in size. The transverse processes of the first five or six are relatively large; behind this they quickly disappear. =Hæmal arches= (or chevron bones) in the form of a =V= or =Y= occur ventrally at the intercentral junctions of the third, fourth, and fifth usually. They transmit the middle coccygeal artery, which passes between pairs of ventral tubercles further back. [Illustration: FIG. 118.—SIXTH CERVICAL VERTEBRA OF DOG, LEFT VIEW. _a_, Ventral plate, _b_, lateral part of transverse process; _c_, foramen transversarium; _d_, anterior articular process; _f_, accessory process; _g_, spinous process; _h_, articular head of body. (Ellenberger-Baum, Anat. d. Hundes.) ] [Illustration: FIG. 119.—FOURTH THORACIC VERTEBRA OF DOG, LEFT VIEW. _a_, Head; _b_, glenoid cavity; _c_, facet for head of rib; _d_, transverse process; _e_, facet for tubercle of rib; _f_, mammillary process; _g_, posterior articular process; _h_, spinous process. (Ellenberger-Baum, Anat. d. Hundes.) ] =Curves.=—A gentle curve, convex ventrally, is formed by the cervical and the anterior part of the thoracic region. The posterior thoracic and the lumbar vertebra form a second curve, concave ventrally. The sacral promontory is well marked. The sacrum and the anterior part of the coccygeal region constitute a third and more pronounced curve, concave ventrally. In long-tailed dogs the sacro-coccygeal region is somewhat =S=-shaped. =Variations.=—Numerical variations are not common except in the coccygeal region. The number of thoracic vertebræ may be twelve or fourteen, with or without compensatory change in the lumbar region. Girard recorded a case with eight lumbar and the usual number of thoracic vertebra. Six lumbar with fourteen thoracic vertebræ have been met with. The first coccygeal sometimes unites with the sacrum. THE RIBS