be allowed to
enter slowly, and without crowding, as otherwise they are not only
likely to get their heads under water, but to throw each other over and
get injured.

The _madrina_, or bell-mare, acts a most important part in a herd
of mules, and is regarded by experienced campaigners as indispensable
to their security. She is selected for her quiet and regular habits.
She will not wander far from the camp. If she happen to have a colt by
her side, this is no objection, as the mules soon form the most devoted
attachment to it. I have often seen them leave their grazing when very
hungry, and flock around a small colt, manifesting their delight by
rubbing it with their noses, licking it with their tongues, kicking up
their heels, and making a variety of other grotesque demonstrations of
affection, while the poor little colt, perfectly unconscious of the
cause of these ungainly caresses, stood trembling with fear, but unable
to make his escape from the compact circle of his mulish admirers.
Horses and asses are also used as bell animals, and the mules soon
become accustomed to following them. If a man leads or rides a bell
animal in advance, the mules follow, like so many dogs, in the most
orderly procession.

"After traveling about fourteen miles," says Bayard Taylor, "we were
joined by three miners, and our mules, taking a sudden liking for their
horses, jogged on at a more brisk pace. The instincts of the mulish
heart form an interesting study to the traveler in the mountains. I
would (were the comparison not too ungallant) liken it to a woman's,
for it is quite as uncertain in its sympathies, bestowing its
affections when least expected, and, when bestowed, quite as constant,
so long as the object is not taken away. Sometimes a horse, sometimes
an ass, captivates the fancy of a whole drove of mules, but often an
animal nowise akin. Lieutenant Beale told me that his whole train of
mules once galloped off suddenly, on the plains of the Cimarone, and
ran half a mile, when they halted in apparent satisfaction. The cause
of their freak was found to be a buffalo calf which had strayed from
the herd. They were frisking around it in the greatest delight, rubbing
their noses against it, throwing up their heels, and making themselves
ridiculous by abortive attempts to neigh and bray, while the calf,
unconscious of its attractive qualities, stood trembling in their
midst."

"If several large troops," says Charles Darwin, "ar