=Remember.= 1. Before the introduction of vaccination, smallpox was one of the most dangerous diseases known. 2. All evidence of history tends to show that vaccination has caused smallpox to become a very mild disease and a comparatively rare one. 3. Successful vaccination repeated at proper intervals will prevent smallpox. 4. Vaccination must be repeated because we do not know just how long the material developed in the body from a single vaccination will last. CHAPTER XXX WHY VACCINATION SOMETIMES SEEMS A FAILURE [Sidenote: What constitutes a successful vaccination] How does it happen that those who have been recently vaccinated sometimes have smallpox? It is _successful_ vaccination that prevents smallpox, not recent vaccination; there is a vast difference between the two. A _successful_ vaccination is one that results in a sore identical with the sores of smallpox. Such a sore is secured only as a result of the action of the germs that cause smallpox. If the arm is red from the shoulder to the wrist and so swollen that you cannot use it for weeks, it does not necessarily mean that you have had a successful vaccination. Such arms are not the result of vaccination itself, any more than a railroad wreck is the result of the fact that there is steam in the engine. The railroad wreck is caused by carelessness on the part of some operator, and the badly inflamed and swollen arm is due to lack of care or knowledge on the part of the vaccinator or the person vaccinated. [Sidenote: Some pretended vaccinations] A fly blister is not a successful vaccination. Such a statement may not seem necessary, until you hear this story. A man showed a sore on his arm, asserting that it was a successful vaccination. He was told that it was nothing but the result of a blister, and not vaccination, and that the work had been done by putting a small bit of blistering plaster on his arm. He admitted this to be the fact, and said that the "doctor" who did it told him that it was a new way of vaccinating. The doctors who say that vaccination will not prevent smallpox belong to the class who use fly blisters and call them vaccinations. When the patient gets smallpox, those who are opposed to vaccinations say that here is an illustration of their claim that vaccination will not prevent smallpox. [Illustration: FIG. 63. How vaccinated arms are sometimes infected.] Some people who honestly think they were vaccinated have smallpox. There are sometimes instances in which a person recently vaccinated with apparent success nevertheless contracts smallpox; there are still other cases in which the disease develops after a vaccination that would not take. Here is an example: