148 VESTIGES OF THE 



not at all developed, a diaphragm and urinary sac 

 (organs wanting in other birds), and feathers approach- 

 ing the nature of hair. Again, the ornithovhynchus 

 belongs to a class at the bottom of the mammalia, and 

 approximating to birds, and in it behold the bill and 

 web-feet of that order ! 



For further illustration, it is obvious that, various as 

 may be the lengths of the upper part of the vertebral 

 column in the mammalia, it always consists of the same 

 parts. The giraffe has in its tall neck the same number 

 of bones with the pig, which scarcely appears to have a 

 neck at all. * Man, again, has no tail ; but the notion of 

 a much-ridiculed philosopher of the last century is not 

 altogether, as it happens, without foundation, for the 

 bones of a caudal extremity exist in an undeveloped 

 state in the os coccygis of the human subject. The limbs 

 of all the vertebrate animals are, in like manner, on one 

 plan, however various they may appear. In the hind- 

 leg of a horse, for example, the angle called the hock is 

 the same part which in us forms the heel ; and the horse, 

 and all other quadrupeds,' with the almost solitary ex- 

 ception of the bear, walk, in reality, upon what answers 

 to the toes of a human being. In this and many other 

 quadrupeds the fore-part of the extremities is shrunk up- 

 in a hoof, as the tail of the human being is shrunk up in 

 the bony mass at the bottom of the back. The bat, on 

 the other hand, has these parts largely developed. The 

 membrane, commonly called its wing, is framed chiefly 

 upon bones answering precisely to those of the human 

 hand ; its extinct congener, the pterodactyle, had the same 

 membrane extended upon the fore-finger only, which in 

 that animal was prolonged to an extraordinary extent. 



* D'Aubenton established the rule, that all the viviparous quad- 

 rupeds have seven vertebrae in the neck. 



