CLASSIFICATION AND CREATION. 69 
Reptile, — or be balanced on two legs, while the 
front limbs become wings, as in Birds, — or be 
raised upon four strong limbs terminating in paws 
or feet, as in Quadrupeds,— or stand upright 
with head erect, while the limbs consist of a pair 
of arms and a pair of legs, as in Man, — does not 
in the least affect that structural conception un- 
der which they are all included. Every Verie- 
brate has a backbone; every Vertebrate has a 
solid arch above that backbone and a solid arch 
below it, forming two cavities,—no matter 
whether these arches. be of hard bone, or of carti- 
lage, or even of a softer substance; every Verte- 
brate has the brain, the spinal marrow or spinal 
cord, and the organs of the senses in the upper 
cavity, and the organs of digestion, respiration, 
circulation, and reproduction, in the lower one; 
every Vertebrate has four locomotive appendages 
built of the same bones and bearing the same re- 
lation to the rest of the organization, whether 
they be called pectoral and ventral fins, or legs, 
or wings and legs, or arms and legs. Notwith- 
standing the rudimentary condition of these limbs 
in some Vertebrates and their difference of ex- 
ternal appearance in the different groups, they 
are all built of the same structural elements. 
And even where they seem wanting, as in Ser- 
pents, a minute study of the gradual reduction 
of the locomotive appendages in various groups 
