Remember. 1. The germs that cause diphtheria always come from some person or animal that carries diphtheria germs. 2. Diphtheria is always caused by the diphtheria germ, and the diphtheria germ cannot cause any other disease. 3. People are quarantined to prevent other people from getting the disease. 4. If there is diphtheria in your neighborhood, and your throat becomes sore, have the doctor examine it. 5. Every person who has been staying in a house where there is a case of diphtheria should have his throat examined to make sure he is not carrying germs. 6. Never play with dogs or cats when you have a contagious disease. 7. People who do not obey quarantine regulations cause a great deal of suffering and many deaths.
[CHAPTER XXIV]
THE CURE OF DIPHTHERIA
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.
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.