As a rule, then, as was stated, the voice of the male differs
from the voice of the female, in animals where the voice admits of a
continuous and prolonged sound, in the fact that the note in the
male voice is more deep and bass; not, however, in all animals, for
the contrary holds good in the case of some, as for instance in
kine: for here the cow has a deeper note than the bull, and the calves
a deeper note than the cattle. And we can thus understand the change
of voice in animals that undergo gelding; for male animals that
undergo this process assume the characters of the female.