THIRD GRAND DIVISION 
OF THE 
ANIMAL KINGDOM. 
THE ARTICULATED ANIMALS. 
This third general form is altogether as characteristic as 
that of the vertebrated animals ; the skeleton is not interior, 
as in the latter, but it is not reduced to a nullity, as in the mol- 
lusca. The articulated rings which surround the body, and 
frequently the limbs too, supply its place ; and as they are 
almost always sufficiently hard, they can afford all the neces- 
sary points of support for locomotion ; so that we find in this 
division, as in the vertebrated, the different movements of 
walking, running, leaping, swimming, and flying. It is only 
the families destitute of feet, or whose feet have only soft and 
membranaceous articulations, which are confined to the move- 
ment of reptation. This external position of the hard parts, 
and that of the muscles in their interior, reduce each articu- 
lation to the form of a case, and allow it only two kinds of 
motion. When it is attached to the neighbouring articulation 
by a firm juncture, which happens in the limbs, it is fixed there 
by two points, and can never move, only by ginglymus, that is 
to say, on a single plane, which requires more numerous arti- 
