Clavicle

Clavicle, an important part of the pectoral girdle of Vertebrates, perhaps most familiarly known in the collar-bone of man and in the merry-thought of birds. It is well developed in those mammals in which the fore-leg or arm is used very strongly and freely, but is poorly developed or absent in many cases, as in Carnivores and Ungulates. In most flying birds it is strong, and often fused to the breast-bone ; in the ostrich tribe it is rudimentary or absent. It is not a prominent bone in reptiles, being absent in snakes and crocodiles, apparently continuous with the scapula in tortoises, and in fact only well seen in the majority of lizards. A 'clavicle' is also to be seen in most Amphibia, though its exact relations are much disputed. A prominent part in the girdle of ordinary bony fishes is also called the 'clavicle,' but it is not certain that it corresponds to that of higher vertebrates. Of the clavicle generally it may be said that it is a paired bone superadded from the skin as an auxiliary to scapula and coracoid, that its position is ventral and anterior to the coracoid, and that it is often associated with an interclavicle. See BIRD, BONE, SKELETON ; also Huxley's Anatomy of the Vertebrate Animals, and other works on Comparative Anatomy, such as those of Gegenbaur and Wiedersheim (translated by Professors Bell and Parker). There is a separate article on the human COLLAR-BONE (q.v.).