of cattle which were covered with the loathsome bloodsuckers; and in a
couple of months every tick would be dead. The worst animal foes of
man, indeed the only dangerous foes, are insects; and this is
especially true in the tropics. Fortunately, exactly as certain
differences too minute for us as yet to explain render some insects
deadly to man or domestic animals, while closely allied forms are
harmless, so, for other reasons, which also we are not as yet able to
fathom, these insects are for the most part strictly limited by
geographical and other considerations. The war against what Sir Harry
Johnston calls the really material devil, the devil of evil wild
nature in the tropics, has been waged with marked success only during
the last two decades. The men, in the United States, in England,
France, Germany, Italy--the men like Doctor Cruz in Rio Janeiro and
Doctor Vital Brazil in Sao Paulo--who work experimentally within and
without the laboratory in their warfare against the disease and death
bearing insects and microbes, are the true leaders in the fight to
make the tropics the home of civilized man.

Late on the evening of the second day of our trip, just before
midnight, we reached Concepcion. On this day, when we stopped for wood
or to get provisions--at picturesque places, where the women from
rough mud and thatched cabins were washing clothes in the river, or
where ragged horsemen stood gazing at us from the bank, or where dark,
well-dressed ranchmen stood in front of red-roofed houses--we caught
many fish. They belonged to one of the most formidable genera of fish
in the world, the piranha or cannibal fish, the fish that eats men
when it can get the chance. Farther north there are species of small
piranha that go in schools. At this point on the Paraguay the piranha
do not seem to go in regular schools, but they swarm in all the waters
and attain a length of eighteen inches or over. They are the most