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.