=Articulation between the Axis and Atlas.=--The =articular capsule= is large and loose, being attached to dorsal and ventral borders of the atlas, about the articular surfaces of the axis, and to the cranial projection of the spine of the atlas. It also passes craniad along the ventral side of the dens and communicates here with the capsule of the atlanto-occipital articulation. In the dorsal part of the capsule a short strong ligamentous strand is developed, connecting the caudal border of the dorsal arch of the atlas with the tip of the cranial projection of the spinous process of the axis. [Illustration: FIG. 14.--LIGAMENTS OF THE ODONTOID PROCESS OR DENS. First three cervical vertebræ and base of the skull, with dorsal surface removed. _a_, ligamentum longitudinale posterius; _b_, transverse ligament of the atlas; _c_, ligamenta alaria; _d_, odontoid process; _e_, occipital condyles; 1, 2, 3, the first three cervical vertebræ; 4, basal portion of the occipital bone.] The dens or odontoid process is held in place by the =transverse ligament= (Fig. 14, _b_) of the atlas, which passes across the process as it lies within the vertebral canal of the atlas. The transverse ligament is attached at its two ends to the medial surface of the sides of the atlas at about the region where the dorsal and ventral arches of the atlas unite. From the cranial end of the odontoid process the two =ligamenta alaria= (Fig. 14, _c_) diverge craniolaterad to the rough ventromedial angle of the condyles of the occipital bone. =II. RIBS. COSTÆ= (Figs. 1 and 15.) The cat has thirteen pairs of ribs. One of the fifth pair (Fig. 15) may be taken as typical. It is a curved flattened rod of bone attached at its dorsal end to the vertebral column, and at its ventral end to a cartilage (=costal cartilage=, Fig. 15, _f_) which serves to unite it to the sternum. The most convex portion of the bone is known as the =angle= (_e_). Each rib presents a convex lateral and a concave medial surface, a cranial and a caudal border. The borders are broad dorsad and narrow ventrad, while the surfaces are narrow dorsad and broad ventrad. The rib has thus the appearance of having been twisted. The rib ends dorsad in a globular head or =capitulum= (_a_), by which it articulates with the costal demifacets of two contiguous thoracic vertebræ. Between the capitulum and angle on the lateral surface is an elevated area, the =tubercle=, marked by the smooth tubercular facet (_c_) for articulation with the transverse process of a vertebra. The constricted portion between the head and tubercle is known as the =neck= (=collum=) (_d_). The angle is marked by a projecting process (_e_) (=angular process=) on its lateral border, for attachment of a ligament. [Illustration: FIG. 15.--FIFTH RIB OF LEFT SIDE, CRANIAL VIEW. _a_, head; _b_, tubercle; _c_, tubercular facet; _d_, neck; _e_, angle, with angular process; _f_, cartilage.]