CLAVICLE, or COLLAR-I30:CE, a bone which, in conjunction with the scapula (q.v:) or blade-bone, forms the shoulder. It derives its name from the Latin word elavis, in consequence of its resemblance to the key used by the Romans. As reference to the figure shows, it is placed horizontally at the upper and lateral part of the thorax, imme diately above the first rib, and it articulates internally with the upper border of the sternum (q.v.) or breast-bone, and externally with the acromion process (or highest point) of the scapula.
Its chief office is to keep the shoulders well separated and steady, and to afford a fulcrum by which the muscles (the deltoid and great pectoral) are enabled to give lateral movement to time arm. Accordingly, it is absent in those animals in which the move ment of the fore-limbs is only backwards and forwards (in one plane) for the purpose of progression, as in the pachydermata, ruminantia, and while it is present in all quadrumana and in those of the rodentia in which the anterior extremities are used for prehension as well as motion, as the rat, 'squirrel, and rabbit; and in the cheiroptera and insectivora, as the bat, mole, and hedgehog. In the mole it occurs in the form of a cube, being very short and broad, and of extreme length. In many of the carnivore (the cat, for example), the C. is present in the rudimentary form of a small bone suspended (like the hyoid bone in the neck) amongst muscles, and not connected either with the sternum or with the scapula. In birds, where great resistance is required to counteract the tendency of the enormous pectoral muscles to approximate the shoul ders, the clavicles are large and united at an angle in the median line (just above the anterior end of the sternum) into a single bone, anatomically known as the " furculum," but popularly recognized as "the merry-thought." In this class of animals, additional, and even more efficient, support to the anterior extremity is afforded by the extension of the corticoid process of the scapula into a broad thick bone called the "corticoid bone" (q.v.), which extends to the sternum. It is unnecessary to trace the various modi
fications which this bone presents in reptiles and certain fishes.
In the human subject, the C. being exposed to the full force of blows or falls upon the shoulder, and not being easily dislocated in consequence of its being well secured at both ends), is very frequently broken.
Ossification takes place in the C. earlier than in any other bone, commencing as early as the 30th day after conception, according to Beclard; and at birth it is ossified in nearly its whole extent. Mr. Humphrey (in his admirable Treatise on the HUMan, Skeleton) sug gests that the early ossification of this bone is a provision on the part of nature to pre vent it from being fractured at birth in case of difficult labor.
Much important anatomical and physiological matter in connection with this bone will be found in Humphrey's work above cited, and in a memoir which he has recently published in the transactions of the Cambridge philosophical society; in Owen, On the Nature of Limbs; and in Struthers, Osteological Memoirs, No. 1, The Clavicle.
CLAVICOR'NfS (Lat. club-horned), a great family of coleopterous insects, of the section pentamera, distinguished by the club-shaped termination of the autunite, which are longer than the maxillary palpi. Most of the beetles of this family feed on animal substances, and many of them, and particularly their larva;, find their appropriate food in substances undergoing decay. It contains many genera, divided into groups (tribes), histeroides, silphales, Burying beetles and the bacon beetle may be men tioned as examples of it.