he infection is not direct, that is, the tick does not feed on one
host then pass to another carrying the disease germs with it. Unlike
many other ticks the Texas fever tick does not leave its host until it
is fully developed. When the female is full grown and gorged she drops
to the ground and lays from 2,000 to 4,000 eggs which soon hatch into
the minute "seed-ticks" which make their way to the nearest blade of
grass or weed or shrub and patiently wait for the cattle to come along.

If the mother tick had been feeding on an animal that was infected with
the Texas fever parasite, her body was filled with the minute organisms
of which some found their way into the eggs so that the young ticks
hatching from them were already infected and ready to carry the
infection to the first animal they fed upon.

It took many years of hard patient work to learn all this, but the
knowledge thus obtained cleared up much of the mystery in connection
with the occurrence of the fever in the north and, as we shall see,
suggested the possibility of other diseases being communicated in the
same way.

It was found that the southern cattle in the region where the ticks
occur normally, usually have a mild attack of the disease when they are
young and although they may be infected with the parasite all the rest
of their lives it does not affect them seriously. These cattle are
almost always infected with ticks, and when taken north where the ticks
do not occur naturally and where the cattle are therefore non-immune,
some of the mature ticks drop to the ground and lay their eggs which in
a few weeks hatch out and are ready to infect any animal that passes by.
The northern cattle not being used to the disease soon sicken and die.

It is estimated that the annual loss due to this disease and the ravages
of the tick in the United States is over $100,000,000, so of course most
determined efforts are being made to stamp it out. Formerly various
devices for dipping the tick-infested cattle into some solution that
would kill the ticks were resorted to, but it was always expensive and
never very satisfactory. The immunizing of the cattle by inoculating
them when they were young with infected blood has been practised. Very
recent investigations have shown that it is possible and practicable to
rid pastures of ticks by a system of feed-lots and pasture rotation. The
aim is to have as many of the ticks as possible drop to the ground on
land where they m