some

have abundance of feathers, others have
only a small quantity. It happens further that some have parts that
others have not: for instance, some have spurs and others not, some
have crests and others not; but as a general rule, most parts and
those that go to make up the bulk of the body are either identical
with one another, or differ from one another in the way of contrast
and of excess and defect. For 'the more' and 'the less' may be
represented as 'excess' or 'defect'.