If you had very magnifying eyes and could see things so enlarged that
these little creatures seemed to {62} you to be an inch long, and if
you looked down into the soil, it would seem to you to be an
extraordinarily wonderful place. The little grains of soil would look
like great rocks and on them you would see creatures of all shapes and
sizes moving about, and feeding on whatever was suitable to them, some
being destroyed by others very much larger than themselves, some
apparently dead or asleep, yet waking up whenever it becomes warmer or
there was a little more moisture. You would see them changing useless
dead roots and leaves into very valuable plant food; indeed it is they
that bring about the changes observed in the experiments of Chap. VI.
Occasionally you would see a very strange sight indeed--a great
snake-like creature, over three miles long and nearly half a mile
round, would rush along devouring everything before it and leave behind
it a great tunnel down which a mighty river would suddenly pour, and
what do you think it would be? What you now call an earthworm and
think is four inches long, going through the soil leaving its burrow
along which a drop of water trickles! That shows you how tiny these
little soil creatures are.

These busy little creatures are called micro-organisms because of their
small size. But they are not all useful. Some can turn milk bad as we
have already seen, and therefore all jugs and dishes must be kept clean
lest any of them should be present. Others can cause disease. It has
happened that a child who has cut its finger and has got some soil into
the cut, and not washed it out at once, has been made very ill. You
may sometimes notice sheep limping about in the fields, especially in
damp fields; an organism gets into the foot and causes trouble.

{63}

SUMMARY. The soil is full of living things, some large like earth
worms, others very small. Earthworms are very useful: they make
burrows in the soil, thus allowing air and water to get in: they drag
in leaves and they keep on covering the surface with soil from below.
Besides these and the other large creatures, there are micro-organisms
so small that they cannot be seen without a very good microscope: they
live and breathe and require air, water and food. Some are very useful
and change dead parts of plants or animals into valuable plant food.
Almost anything that can be consumed by fire can be consumed by them.
O