. Cassell's natural history. Animals; Animal behavior. A y ATOMY OF A I Kcc'lof Stii "boflv," and others directed forwards and backwards, so as to connect each vertebra with its neigh- bours ; and lastly, a lower arch, the two halves of which are not connected below, but are converted into the more or less long ribs. As these vertebrne are so small it is clear that if their spines were long the free movement of the neck would be greatly impeded, and they are therefore in many cases little more than projecting processes. This free movement is further greatly aided by the charac
. Cassell's natural history. Animals; Animal behavior. A y ATOMY OF A I Kcc'lof Stii "boflv," and others directed forwards and backwards, so as to connect each vertebra with its neigh- bours ; and lastly, a lower arch, the two halves of which are not connected below, but are converted into the more or less long ribs. As these vertebrne are so small it is clear that if their spines were long the free movement of the neck would be greatly impeded, and they are therefore in many cases little more than projecting processes. This free movement is further greatly aided by the characters of the two faces of the body (or centrum) of each vertebra; the face of each is saddle-shaped, that is to say, the anterior face is concave from side to side, and convex from above downwards, while the reverse of this is seen on the posterior face; in addition to this the vertebrse are sejjarated by a disc of cartilage from one another. The region of the neck is, broadly speaking, distinguished from that which succeeds it by the fact that the ribs connected with its vertebrse do not reach to the sternum, or breast-bone. In all birds which are capable of flight this dorsal region has its parts firmly united togetl'.er, and the same holds for the parts which follow, till we reach the region of the tail, where the more anterior vertebra? are movable on one another, so as, perhaps, to serve in aid of the steering organ formed by the rectrices, or feathers (co). In all living birds the caudal vertebrse are a good deal shorter than the body, but Ln the fossil Archwopteri/x they are longer. The only important point to note with regard to the ribs, is the presence on some of them of backwardly directed hooked processes (up, fig. on p. 241), which aid in giving firmness to the thoracic region. The number of ribs is variable, but there is never a large number connected with the dorsal vertebrje, thei-e ai-e in some Carnivora, in Hyrax, and in the Horse. The fore and hind limbs a
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