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.
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.
Fig. 56. Showing the number of deaths in 100 cases of diphtheria when antitoxin is used on the first, second, third, fourth, and fifth days.
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?
How antitoxin saves lives