1564 THE STORY OF THE UNIVERSE 



prolongation, and the ribs are found in that of the 

 Cetacea. The thorax is carried very much forward, 

 especially in the whale, and the neck is so short as to 

 be scarcely recognizable: for the object of the con- 

 formation is here, as in that of the fish, to allow free 

 scope for the movements of the tail and ample space 

 for the lodgment of its muscles. For the purpose 

 of giving greater power and more extensive attach- 

 ment to these muscles, the transverse processes of the 

 dorsal and lumbar vertebrae are expanded both in 

 length and breadth, and, being situated horizontally, 

 offer no impediment to the vertical flexure of the 

 spine. For the same reason the ribs are continued 

 in a line with the transverse processes, and articulated 

 with their extremities, thus giving still further 

 breadth to the trunk. 



As there is a total absence of hinder extremities, 

 so there is no enlargement of any of the vertebrae 

 corresponding to a sacrum, and the caudal vertebrae 

 are uninterrupted continuations of those of the trunk. 

 They develop, however, parts which are met with 

 only among fishes and reptiles, namely, arches 

 composed of inferior leaves and spinous processes, 

 inclosing and giving protection to a large artery. 

 Although the bones of the legs do not exist, yet there 

 are found, in the hinder and lower part of the trunk, 

 concealed in the flesh, and quite detached from the 

 spine, two small bones, apparently corresponding to 

 pelvic bones, for the presence of which no more prob- 

 able reason can be assigned than the tendency to pre- 

 serve an analogy with the more developed structures 

 of the same type. 



