CHAPTER II. 



SOME INTERNAL STRUCTURES 

 VERTEBRAL COLUMN 



THE series of bones which constitute the vertebral 

 column or backbone in the whales offer a number 

 of peculiarities distinctive of the group. 



Like all other mammals (with inconsiderable ex- 

 ceptions, Manatee, Sloth) the neck vertebrae are but 

 seven in all. But in the whales these vertebrae are 

 very generally partially or entirely fused together 

 (Fig. 8), the degree of fusion also varying from species 

 to species. Hand in hand with this melting together 

 of the vertebrae goes a thinning of the actual vertebrae 

 themselves, so that the neck region of the Cetacea 

 is excessively short. They are the shortest necked 

 of all mammals. It is, however, important to em- 

 phasise the fact that the mysterious and "perfect" 

 number seven, which characterises all mammals (with 

 the very few exceptions already noted), is preserved 

 in these exceedingly short-necked creatures. It is 

 by a reduction of individual vertebrae, not by a 

 dropping out of one or more in the series, that the 

 neck is reduced in length. At first sight it is tempting 

 to put down the remarkable consolidation of these 



37 



