ench, and there to have spread,
because of the peculiar fitness of the creature to the climate and the
employment it had to endure in that part of America. The mule has the
peculiar advantage that it is on the average as large as the horse, is
nearly as quick-footed when walking, and has at the same time a
considerable share of the patient endurance to hard labor and scant
fare which characterizes the donkeys. It matures somewhat more speedily
than its nobler kinsman, being ready to meet severe strains perhaps a
year earlier. Unless unconscionably abused, its period of fitness for
hard work endures about one-third longer, often lasting for thirty
years. It is singularly exempt from disease, its sturdy frame
withstanding rude usage until the old age time.

[Illustration: In the Circus]

The mule is especially interesting to the naturalist for the reason
that it affords the only certain case in which a hybrid has proved
decidedly serviceable to man. It is not unlikely that a similar mixture
of the blood of two species occurs in our ordinary cats, and it may
exist in the case of the dog and in some of the domestic birds; but so
far as we know, there has been no other useful result from the
hybridizing, if it has occurred. Moreover, the mule is unique for the
fact that the animal is distinctly stronger for its weight, and more
enduring than either species which his blood combines. In fact, there
is no product of man's industry in relation to domesticated animals
which is more interesting than this singular creature. At present, its
use appears to be going out of vogue; the evidence goes to show that
the hybrid has no place in the affections of mankind, and that it is
only likely to be kept in its use in tropical countries, and
particularly in regions where the beasts have to be under the care of
slaves or other negligent folk. It is a singular fact in connection
with this hybrid, that it is nearly absolutely sterile, there being
only two or three cases on record in which they have proved fecund. It
seems, however, possible that if these rare instances of continued
breeding were to be duly used, an intermediate species might be
permanently established. This is, indeed, one of the most important
lines for experiment which could be undertaken by an institution
devoted to the study of problems relating to domestication.

It is commonly thought that a mule is a stupider creature than the
horse; but I have never found a person