46 A BOOK OF WHALES 



lates but one pair of ribs, the first. It is a matter 

 of interest to inquire into the exact nature of this 

 simple bone, which is all that is left of the sternum 

 in the Mystacoceti. In many mammals the sternum 

 in the adult is no more than a single solid bone ; but 

 here the apparent simpleness of the sternum is due 

 to the co-ossification of originally separate elements. 

 The articulation of several pairs of ribs is a clue to 

 the number of those elements. Now as in the Right 

 whale and Rorquals but one pair of ribs articulates with 

 the small sternum, we should infer that it is the front 

 piece of the sternum that piece which has been 

 fancifully termed the manubrium the handle of the 

 sword-shaped sternum. It may be remarked here 

 that the end piece of the sternum is generally 

 called the processus ensiformis, or ensiform piece, 

 thus completing the analogy derived from the com- 

 parison with the sword. It is extremely important 

 to notice that there is evidence here too that the 

 shortening of the sternum has really taken place, and 

 that comparatively recently. In the first place, Sir 

 William Turner found in that giant among giants 

 the huge Rorqual, Balcenoptera sibbaldii, a second 

 piece of sternum identified by him with the ensiform 

 cartilage, or xiphisternum as it is sometimes called ; 

 and, in the second place, the well-known cetologist 

 the late Prof. Eschricht, of Copenhagen found 

 in a whalebone whale that a fibrous band arising 

 from the end of the sternum was attached to the 

 second and third ribs. This is clearly a rudiment 

 of a posterior prolongation of the sternum. 



