In Gloucester, England, there used to be a great many people who did not believe in vaccination, though it is doubtful if they themselves could have explained why they did not. They seem to have been much like the man who, when asked, "What do you think of this?" replied, "I don't know anything about it, but I am against it." In 1890 Gloucester had a population of 42,000 people, most of whom had never been vaccinated. In the latter part of 1895, smallpox broke out. Quarantine was strictly carried out, but the disease continued to spread. As the people saw the number of victims rapidly increasing, many of them concluded that they had rather be vaccinated than have smallpox, even though they did not really believe in vaccination. By the first of April, 1896, over 36,000 people had been vaccinated in Gloucester, and by the first of August there was not a case of smallpox in the city. But what had happened in the meantime? There had been 1,979 cases of smallpox; a very large amount of money had been expended in quarantining; hundreds of persons had been disfigured for life; and 439 lives had been lost. And all this simply because the people did not believe in vaccination. Quarantining smallpox is a most expensive luxury, which may possibly retard the progress of this disease, but was never known to check an epidemic of it. Every epidemic of smallpox during the last one hundred years has been checked by vaccination. [Sidenote: Why some diseases do not return] There are certain diseases which you are not likely to have more than once; one attack protects against another. Why and how does one attack of a certain disease protect against another? When a person is taken sick with one of these diseases, the cells of his body immediately begin to make a substance called antitoxin. We learned something about antitoxin when we were studying diphtheria. In diseases like scarlet fever, measles, and smallpox, in which one attack protects against another, the antitoxin that is formed in the body when you are sick stays there for a long time, in some cases as long as you live. While this antitoxin is present in the blood, the cause of the disease cannot live in the body; hence you cannot have the disease again. After some diseases this antitoxin seems to disappear from the blood in a short time; after others, it seems to remain for several years; and after still others it remains as long as you live. After diphtheria it stays in the blood only a short time, so that one may have diphtheria a second time within a few years. Some people have smallpox, measles, or scarlet fever a second time, but with most people these diseases never return.