When animals arrive at maturity,

their properties are as above
stated; but they differ greatly from one another in their growth
towards maturity. For instance, man, when young, has his upper part
larger than the lower, but in course of growth he comes to reverse
this condition; and it is owing to this circumstance that-an
exceptional instance, by the way-he does not progress in early life as
he does at maturity, but in infancy creeps on all fours; but some
animals, in growth, retain the relative proportion of the parts, as
the dog. Some animals at first have the upper part smaller and the
lower part larger, and in course of growth the upper part gets to be
the larger, as is the case with the bushy-tailed animals such as the
horse; for in their case there is never, subsequently to birth, any
increase in the part extending from the hoof to the haunch.