Chapter XXIV: The Cure of Diphtheria

[Sidenote: Nature of diphtheria poison]

The germs of diphtheria do not get into the blood through the skin, but grow on the surface of the mucous membrane (skin of the throat), and there produce a poison that gets into the blood through this membrane. It is this poison that makes you sick, and it is called a _toxin_. You already know that when people have diphtheria, they are sometimes very sick and sometimes only slightly sick, and that the germ can live in some throats without causing any ill effects whatever.

[Sidenote: How diphtheria toxin is fought]

As soon as the diphtheria germ begins to grow in a throat, the little cells of the body begin to make a certain substance and to pour it into the blood. This substance we call _antitoxin_, which means opposed to the toxin in the blood. If the little cells make the substance fast enough, the germs will stop growing, or in some cases they never really get started growing, because they cannot exist where there is much antitoxin. Antitoxin looks like clear water. The following experiment will show you something that acts in very much the same way that antitoxin does.

If you take a solution of litmus that is made alkaline, it will be very blue, like indigo; but if you drop a few drops of lemon juice into this solution it will turn red.[3] Lemon juice is acid, and is just the opposite of alkali. Now, if you put a few drops of ammonia, which is alkali, into the red solution, it will turn blue again. If you put a little more lemon juice, very carefully, drop by drop, into the blue solution, it will gradually turn lighter, until it is entirely clear.

[Sidenote: How antitoxin acts]

We will suppose that the blue is due to the toxin produced by the diphtheria germ, and that the lemon juice is the antitoxin produced by the cells in the body. If the antitoxin is made fast enough, the blue disappears; but if the toxin is made faster than the antitoxin, the blue remains. It is the same way in the body, only it is not litmus and acids and alkalies that we have to deal with. If the toxin is made faster than the antitoxin, the germs grow, and we get sicker and sicker; but if the antitoxin is made faster than the toxin, then the germs cannot grow, and we soon get well, or perhaps do not get sick at all.

[Sidenote: How antitoxin was discovered]

Doctors knew that this was what happened, but for a great many years they could not discover the composition of the antitoxin that is made in the body. One day a doctor suggested, "If we cannot find out the chemical nature of this thing that is made in the body, why can we not make it in the body of some animal and then use the blood of the animal?" And that is just what they did. They put diphtheria germs into beef tea, and let them grow very fast and make all the toxin they could. Then the doctors strained the germs out by passing the beef tea through a fine filter, in this way getting the poison, and not the germs. Then they gave a strong, healthy horse a small quantity of this poison; they did not feed it to him, but injected it into his blood. Of course the horse was sick for a while, but soon he began to get well again, for the cells in his body immediately went to work making antitoxin.

When the horse was well, the doctors gave him more of the poison; this time he was not so sick and got well even more quickly. This treatment with toxin was repeated in gradually increasing doses until the poison did not affect the horse at all. Then the doctors said, "His blood is full of antitoxin, and we will see what it will do when injected into some other animal." So they drew off some of the horse's blood and took out all the little red cells, leaving nothing but the clear fluid of the blood. They planted diphtheria germs in a rabbit's throat, and when the rabbit became very sick, they gave him some of the antitoxin from the horse. The rabbit immediately got well. Afterward they gave some of this antitoxin to a little boy who was very sick with diphtheria, and he, too, got well. Ever since then the doctors have been saving many lives by the use of antitoxin.

[Sidenote: Evidences that antitoxin saves lives]

Someone may ask, "How do we know that it is the antitoxin that saves lives?" In just this way: before we knew anything about antitoxin, about half of all the people with diphtheria died; but since we have had antitoxin, only about twelve die out of every hundred who have this disease. More than this, we know that when the antitoxin is given within the first twenty-four hours after the patient is taken sick, there is only about one death for every one thousand cases of diphtheria. Do you not think that this is strong proof that antitoxin saves lives?

[Sidenote: How antitoxin saves lives]

Antitoxin saves lives not only by curing those who have diphtheria, but by preventing others from having it. If a person who has been where there is a case of diphtheria is given a dose of antitoxin, he will not have the disease, because his blood will contain enough antitoxin to destroy the diphtheria toxin present. If you will watch a careful doctor when he makes his first visit to a case of diphtheria, you will notice that, as soon as he gets through treating the patient, he gives all members of the family who have been near the patient a dose of antitoxin to keep them from getting sick.

[Sidenote: Antitoxin not a poison]

Some people may tell you that antitoxin is a poison and should not be used. The statement that it is in itself a poison is true. But it is also true that in your body there are many things that would poison you if you got too much of them. For instance, there is a gland in your throat (the thyroid) which secretes a substance that is necessary for your health, but if you were to take the secretion of ten such glands it would kill you at once. Now, if the cells in your body make antitoxin when you have diphtheria, it is probable that antitoxin is the very thing needed. And if you can help these cells by giving them antitoxin, ready-made, does it not seem a reasonable thing to do? People who give the name of poison to a substance which is known to have saved many lives are not worthy of attention. Anything may prove a poison if taken in excess; too much play will prove a poison, and too much work also.

=Questions.= 1. What is the poison of diphtheria called? 2. What
is antitoxin? 3. Compare the action of antitoxin on the blood
with the action of an acid on the litmus solution. 4. Tell about
the discovery of antitoxin. 5. How do we know that antitoxin
saves lives? 6. How does antitoxin prevent diphtheria? 7. Why
should antitoxin not be regarded as a poison?

=Remember.= 1. Antitoxin is what the cells in your body make
when you have diphtheria. 2. By using the antitoxin taken from
a horse, you save your own cells the struggle necessary to make
it fast enough to kill the diphtheria germs. 3. If you have
diphtheria, and antitoxin is given promptly, you will get well.
4. If you have been exposed to diphtheria, antitoxin will prevent
your having the disease. 5. Antitoxin is no more a poison than
are many other medicines.