THE VEGETABLE AJH 3 ANIMAL KINGDOMS. 101 



are fully developed in fishes, being required by them for 

 She respiration of aerated waters, but which are not need- 

 ed by the atmosphere-breathing marsupials. We have 

 also the peculiar form of the sternum and rib-bones of the 

 lizards represented in the mammalia in certain white car- 

 tilaginous lines traceable among their abdominal muscles. 

 The struphionidae (birds of the ostrich type) form a link 

 oetween birds and mammalia, and in them we find th« 

 A'ings imperfectly or not at all developed, a diaphragm 

 and urinary sac (organs wanting in other birds,) and 

 feathers approaching the nature of hair. Again, the orni- 

 thorynchus belongs to a class at the bottom of the mam- 

 malia, and approximating to birds, and in it behoid the 

 bill and the web-feet of that order ! 



For farther illustration, it is obvious that, various as 

 may be the lengths of the upper part of the vertebral col 

 umn 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 cau- 

 dal extremity exist in an undeveloped state in the os coc- 

 cygis of the human subject. The limbs of all the verte- 

 brate 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 quad- 

 rupeds, with almost the solitary exception of the bear, 

 walk, in reality, upon what answer 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 a 

 human being is shrunk up in the bony mass at the bot- 

 tom of the back. The bat, on the other hand, has these 

 parts largely developed. The membrane, commonly call- 

 ed its wing, is framed chiefly upon bones answering pre- 

 cisely to those of the human hand ; its extinct congener, 

 the pterodactyle, had the same membrane extended upon 

 he fore-finger only, which in that animal was prolonged 

 to an extraordinary extent. In the paddles of the whale, 

 and other animals of its order, we see the same bones as 

 in the more highly developed extremities of the land 



* Daubenton established the rule, that all the viviparous quad 

 rupeds have seven vertebras in the neck. 



