THE SKELETON. 275 



on the limbs of Articulated Animals, and the muscular 

 system, the contractile fleshy bands of which are attached 

 to the inside of the chitinous tubes, is correspondingly 

 jointed in an extremely varied manner. The case is exactly 

 reversed in Vertebrates. In these alone an internal hard 

 skeleton develops ; an inner cartilaginous or bony frame 

 to which the fleshy muscles are externally attached, and in 

 which they find a firm support. This bony frame forms a 

 combined lever-apparatus, a passive apparatus of motion. 

 The hard parts of this, the arms of the lever, or the 

 bones, are moored against each other by the active movable 

 muscular bands, as by hawsers. This admirable locomotive 

 apparatus, and especially its firm central axis, the vertebral 

 column, is quite peculiar to Vertebrates, on account of which 

 the- whole group has long been called that of Vertebrates. 



This internal skeleton, notwithstanding the similarity of 

 its first rudiment, has, however, developed so variously and 

 characteristically in the different vertebrate classes, and in 

 the higher classes forms so complex an apparatus, that 

 Comparative Anatomy finds one of its richest mines in this 

 feature. This was recognized as long ago as the beginning 

 of the century by the older Natural Science, which at once 

 seized these very welcome materials with peculiar pleasure. 

 That science also, which is now called in the higher and 

 more philosophical sense, " Comparative Anatomy," has 

 reaped its richest harvest from this field. The Comparative 

 Anatomy of the present day has studied the skeleton of 

 Vertebrates more thoroughly, and revealed the laws of its 

 formation more successfully, than has been the case with 

 any other system of organs of the animal body. Here the 

 well-known and oft-quoted passage, in which Goethe 



