The stomach and bowels are pale and empty,
and the gall-bladder is distended with bile.

These symptoms seem to indicate what is probably the case, a poison in
the blood, the germ of which enters when the proboscis is inserted to
draw blood. The poison-germ, contained in a bulb at the root of
the proboscis, seems capable, although very minute in quantity, of
reproducing itself, for the blood after death by tsetse is very small
in quantity, and scarcely stains the hands in dissection. I shall
have by-and-by to mention another insect, which by the same operation
produces in the human subject both vomiting and purging.

The mule, ass, and goat enjoy the same immunity from the tsetse as man
and the game. Many large tribes on the Zambesi can keep no domestic
animals except the goat, in consequence of the scourge existing in their
country. Our children were frequently bitten, yet suffered no harm; and
we saw around us numbers of zebras, buffaloes, pigs, pallahs and other
antelopes, feeding quietly in the very habitat of the tsetse, yet as
undisturbed by its bite as oxen are when they first receive the fatal
poison. There is not so much difference in the natures of the horse
and zebra, the buffalo and ox, the sheep and antelope, as to afford
any satisfactory explanation of the phenomenon. Is a man not as much
a domestic animal as a dog? The curious feature in the case, that dogs
perish though fed on milk, whereas the calves escape so long as they
continue sucking, made us imagine that the mischief might be produced by
some plant in the locality, and not by tsetse; but Major Vardon, of the
Madras Army, settled that point by riding a horse up to a small hill
infested by the insect without allowing him time to graze, and, though
he only remained long enough to take a view of the country and catch
some specimens of tsetse on the animal, in ten days afterward the horse
was dead.

The well-known disgust which the tsetse shows to animal excreta, as
exhibited when a village is placed in its habitat, has been observed and
turned to account by some of the doctors. They mix droppings of animals,
human milk, and some medicines together, and smear the animals that are
about to pass through a tsetse district; but this, though it proves a
preventive at the time, is not permanent. There is no cure yet known for
the disease. A careless herdsman allowing a large number of cattle to
wander into a tsetse district loses all except the calves; an