KINDS OF MOTION. 13) 
the more numerous the limbs, and the more equally they 
are distributed on the inferior side of the body, the more 
securely will the centre of gravity be retained within the 
space which these feet include. In the annulose animals, 
termed myriapoda, the feet, which are numerous, and very 
strong in proportion to the size of the body, are so placed, 
that the centre of gravity of the body can never fall beyond 
the surface occupied by them; and consequently, these ani- 
mals may be considered as possessing, in the greatest degree 
of perfection, the qualifications necessary for assuming and 
maintaining a standing position. In many of the true or 
hexapodal insects, the same provision for preserving the 
body in a standing posture may likewise be observed. The 
feet are well qualified, by their strength, for supporting the 
body, and when stretched out, the space which they melude 
is, in general, many times larger than its bulk. 
Among the vertebral animals, standing is an attitude 
practised by the Mammalia and Birds only. Among the 
mammalia, all, except Man, stand on four feet. The body, 
in this case, rests on an extended base; but as the head 
projects more or less in front of the trunk, to which the 
fore-legs are attached, the centre of gravity falls nearer 
these than the hind-legs. They are on that account strong- 
er than these last, to enable them to support this addition- 
al burden, unless in those cases where the hind-legs are 
used for particular kinds of motion. ‘The head is support- 
ed by the cervical ligaments, and by muscles, which vary 
in strength with the weight of the head, and the actions 
which it is required to perform. 
In Man, standing is performed on two legs only. The 
mechanical structure of his body enables him to do this 
without any singular exertion. The weight of his head, 
the weakness of his arms, and the inconvenient length of 
his legs, all prevent him from standing on his four extremi- 
i2 
