i6o 



ELEMENTARY ANATOMY. 



[LESS. 



complexity of the parts which may represent, or most nearly 

 correspond with it in the lower, and especially the lowest, 

 Vertebrates. 



In fact, however, the clavicle of man is made up of four 

 parts, as has been noted. Thus we have 



(1) The body of the bone. 



(2) The acromial end of the clavicle, remaining cartilagi- 

 nous in the young state, called the meso-scapular segment. 



(3) The sternal epiphysis of the clavicle, called the pre- 

 coracoid. 



(4) The inter-articular fibro-cartilage interposed between 

 the clavicle and the sternum, called the omosternum. 



asff" 



FIG 135. INNER PART OF CLAVICLE 



AND PART OF STERNUM OF A SHREW 



Sorex. (After Parker. ) 



cl, sternal part of clavicle ; ec, ep'i- 

 coracoid ; pc, pre-coracoid ; ost, omo- 

 sternum. 



FIG. 136. RIGHT SCAPULA AND 

 SCAPULAR PART OF CLAVICLE OF A 

 SHREW Sorejc. (After Parker.) 



a, acromion ; c, cpracoid ; cl, clavicle ; 

 ma, metacromion ; mss, meso-sca- 

 pular segment. 



Now, inasmuch as the clavicle of man consists of only 

 one conspicuous element, is separated from its fellow clavicle 

 by the sternum, and connected externally with the acromion, 

 it has the general characters of the bone in his class. It 

 may, however, be entirely absent, as in all Cetacea and 

 Ungulata, in many Carnivora and Rodents. 



It may, on the contrary, be very short and rudimentary, 

 and suspended by long ligaments both to the scapula and 

 sternum, as in the Guinea-pig and Rabbit. 



It may be separate from its fellow cf the opposite side and 

 from the sternum, as in the Cassowary and Emeu. 



It may though this is very rare have ultimately coalesced 

 with the coracoid, so as to form a complex single bone of 

 double nature, as in the so-called clavicle of the Mole, which 

 helps to form the articulation of the humerus. 



