On The Gait Of Animals   

right is the same in all, for that from which motion begins is the

same for all, and has its natural position in the same place, and

for this reason the spiral-shaped Testaceans have their shells on

the right, for they do not move in the direction of the spire, but all

go forward in the direction opposite to the spire. Examples are the

murex and the ceryx. As all animals then start movement from the

right, and the right moves in the same direction as the whole, it is

necessary for all to be alike right-handed. And man has the left limbs

detached more than any other animal because he is natural in a

higher degree than the other animals; now the right is naturally

both better than the left and separate from it, and so in man the

right is more especially the right, more dextrous that is, than in

other animals. The right then being differentiated it is only

reasonable that in man the left should be most movable, and most

detached. In man, too, the other starting-points are found most

naturally and clearly distinct, the superior part that is and the

front.

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Animals which, like men and birds, have the superior part

distinguished from the front are two-footed (biped). In them, of the

four points of motion, two are wings in the one, hands and arms in the

other. Animals which have the superior and the front parts identically

situated are four-footed, many-footed, or footless (quadruped,

polypod, limbless). I use the term foot for a member employed for

movement in place connected with a point on the ground, for the feet

appear to have got their name from the ground under our feet.

Some animals, too, have the front and back parts identically

situated, for example, Cephalopods (molluscs) and spiral-shaped

Testaceans, and these we have discussed elsewhere in another

connexion.

Now there is in place a superior, an intermediate, and an