FLIES AS CARRIERS OF DISEASE
[Sidenote: How germs get into our bodies]
Disease germs get into our bodies in three principal ways: they are
eaten with our food; they are taken in with the air we breathe; and
they get in through breaks in our skin, even though these breaks be
very small, as when made by the bite of a mosquito or other insect.
[Sidenote: How germs get into our food:]
[Sidenote: (_1_) From the air]
How do germs get into our food or drink? You must remember that
these germs are extremely small, so small that many of them can be
carried by a particle of dust that you can see only in a ray of
sunshine. When the germs become dried, they float about on these
particles of dust, the dust alights on our food, which is moist and
warm, and the germs immediately begin to grow.
[Sidenote: (_2_) From the hands]
Another way by which germs get on food is from the hands through
which it passes. Did you ever think how many people handle an
apple? First, the man who picks it from the tree; then the examiner
in the packing house where apples are taken to see that they are
the right kind to be packed in a certain box. Then it is wiped off
by a boy or girl--handling number three; then it is wrapped in
paper--number four. Next it is packed in a box, but in this case
the paper protects the apple from dirty hands. When the merchant
buys the apples he feels several of them, and puts them out on the
display shelf; this makes handling number five. Everyone who thinks
of buying apples will touch one or more of them, and when they are
sold the clerk handles them again. In other words, every apple goes
through the hands of at least seven people before you get it. Do
you not think it needs washing?
Go into a butcher shop and see how many people will put their dirty
fingers on the meat. Some of them even keep their gloves on when
they do this. Imagine how many germs may be planted on the finger
of a glove.
Our whole method of displaying foods for sale is wrong. The
customer can see the fruits, vegetables, and meats just as well
in a glass case as when they are on an open counter or shelf, and
nothing is gained by poking a dirty finger into a piece of beef, or
by rubbing your hands over the apples. A glass case not only will
protect the fruits and meats from such practices, but will keep out
germ-laden dust and flies whose feet are covered with germs.
[Illustration: FIG. 42. The foot of a fly, highly magnified.]
[Sidenote: (_3_) From flies]
_Probably the most common source of germs on food is the fly._ Did
you ever watch a fly very closely for a long time? Did you ever
happen to see a manure pile early in the morning and notice how
many tiny flies are on it? These flies have just been hatched.
[Sidenote: Breeding places of flies]
Flies like manure because it is the best place they can find in
which to lay their eggs. Each female fly lays about three hundred
eggs. They do not hatch directly into flies, as hen's eggs hatch
into chickens, but when the fly's eggs hatch you find maggots, and
these maggots later hatch into flies.
[Sidenote: The journey of the fly]
Turn over the manure some spring morning, and you will see it full
of white specks. These specks are maggots that will hatch into
flies. Watch the flies as they leave the manure pile and see where
they go. If there is a dead dog or cat or a filthy garbage can
near, they will fly to it. Then they will go into the water-closet
and crawl over the filth there. Their next trip will probably bring
them to the kitchen, where they will crawl over the food. From here
they will go to the cuspidor and take a drink of water, and will
get their feet covered with the dirt that is in the cuspidor. Next
they will try a walk over the nipple of the baby's bottle, or they
will light on your face, or get into the butter or milk.
After the fly has been in dirty places, he "washes" his face and
hands, that is, he rubs his feet together and then rubs them over
his head. Did you ever see a fly wash himself with water? No, you
never did.
[Illustration: FIG. 43. Where a fly has walked; each little spot
represents a growth of germs left by the fly.]
After a fly has made his journey, you would suppose that his feet
would be covered with dirt and germs, and so they are. Not only
does he carry germs on his feet and body but he also eats dirty and
diseased things. Moreover, fly specks contain the germs of disease,
and the fly is not at all particular about where he puts his specks.
[Sidenote: Proof that the fly is a germ carrier]
If you let a fly walk over a culture plate, there will be a growth
of germs wherever his feet touch. A culture plate is simply a
glass plate covered with gelatine or something else in which
these germs like to grow, and where they can easily be seen. Each
germ will multiply so fast that there will soon be a spot of them
large enough to be seen readily with the naked eye. In the picture
showing a culture plate over which a fly has walked (Fig. 43), the
little specks are not single germs, but each speck represents a
growth containing many thousands of germs.
[Illustration: FIG. 44. Flies go from filth to food.]
[Sidenote: How to get rid of the fly:]
How are we going to get rid of flies? We cannot get rid of them
entirely, but there are a great many ways by which we can prevent
there being so many of them, and whereby we may keep them out of
our houses and away from our food.
[Sidenote: (_1_) By removal of manure]
We have learned that flies are always found about horse manure,
because it makes a good place in which to hatch their eggs. If we
could dispose of the manure, there would be one place less for the
fly to lay her eggs. Behind barns we usually find piles of manure.
It is in these heaps that the fly lays her eggs, not in the little
lumps found in the streets. Now, there is no sense in keeping this
great pile of manure about any barn. In towns the manure can be put
into a box with a cover, so that the flies cannot get at it. In the
country every well-managed farm has the barns cleaned out every
day, and it would not be much more trouble for the farmer to throw
the manure into a wagon and take it to the fields with him, than
it is to pile it up beside his barn. If he did this, he would find
that there would be few flies about his house.
[Sidenote: (_2_) By covering garbage cans]
Even if we were to take every particle of manure away as fast as
possible, we should still have some flies, for when flies do not
find manure for their hatching places, they will take the next best
thing. It must be something dirty; clean things will not answer
at all for a fly's home. Next to the manure pile, the fly likes a
dirty garbage can, a dead animal, or anything that is decomposing.
If she cannot find anything better, she will take a rotting apple;
but she does not really like this, and if she cannot find anything
better than an old apple in your yard, she will probably go
elsewhere to lay her eggs.
[Sidenote: (_3_) By keeping clean yards]
We cannot entirely stop the hatching of flies, but if we do
away with the old manure piles, keep fresh manure and garbage
cans covered, and keep our yards free from everything that can
decompose, we shall have very few flies about our houses.
[Sidenote: How to keep flies out of the house]
Since we cannot get rid of all the flies, the next best thing is
to keep the few that may be left out of our houses and away from
our food. This we can do by means of wire screens and netting. Wire
screens are very cheap, and if there are no wire screens on your
house, you should persuade your father to buy some. But a screen
will not keep flies out unless it is kept closed, so do your part
by never leaving the screen door open for a second longer than is
necessary for you to go in or out.
Our houses are not the only places that need screens.
Slaughterhouses, butcher shops, candy stores, grocery stores--every
place where any kind of food is handled or sold--should be
screened. Flies should never be allowed to alight on anything which
is to be eaten.
=Questions.= 1. Name three ways by which germs get into our
bodies. 2. How do germs get into our food? 3. Why should foods be
screened? 4. Trace the fly from his birth-place to our food. 5.
How do we know that flies have germs on their feet? 6. Tell how
we can get rid of most of the flies. 7. How can we keep flies out
of the house? 8. What can boys and girls do to help keep them out?
=Remember.= 1. Always wash an apple, pear, or any other fruit
before you eat it. 2. All foods are handled by many people, and
are not clean until they have been washed. 3. Flies like to live
in dirty places, and their feet and legs are covered with germs;
get rid of the flies. 4. Flies hatch in manure piles and other
dirty places; keep your yard and lot clean so that flies will
have no place to lay their eggs. 5. Put screens on the house to
keep flies out, and keep the screens closed.