Yellow fever was entirely eradicated. In 1904 we had a few cases, and in 1905, a sharp epidemic. In November, 1905, the last case occurred in the city of Panama, and in May, 1906, the last case in the town of Colon. Since that time no cases have originated on the Isthmus. On June 20, 1905, Nehemiah Morgan, a Jamaican negro, employed at La Boca, the southern terminus of the Canal, was admitted to the hospital with symptoms of bubonic plague. The name La Boca has since been changed to Balboa. This man died on June 23, and the autopsy confirmed the diagnosis. On the twenty-sixth, a quarantine was placed against La Boca. Dr. James Perry, of the United States Public Health Service, was placed in charge. He was supplied with a force of four foremen and one hundred laborers, who under his direction did the necessary cleaning and fumigation. This quarantine was kept up until July 15, when it was raised, as there was no further indication of plague or plague-infected rats. Dr. Perry deserves the greatest credit for the efficient way in which he managed to stamp out this infection, so threatening and dangerous to the work. Plague is an infectious disease caused by a well-known germ, the bacillus pestis. It is a disease of the rat, and is transferred from the rat to a human being by the rat flea. Anti-plague measures are, therefore, almost entirely directed toward the destruction of rats. Rigid quarantines are also kept up, so as to prevent human beings sick with the disease from going to uninfected places, and there starting new foci of infection. The measures used against rats are poisons of various kinds, but the rat is one of the most intelligent of animals, and soon learns to avoid poisons. The same thing is true with regard to traps. Rats so rapidly learn about poisons and traps that some writers on anti-plague measures advise that these measures be used only during emergencies, when plague is either present, or there is imminent danger of an outbreak, the argument being that if you use these measures continuously, the rats will become so knowing that you cannot kill them when plague is upon you and they are actually infected. Mr. Le Prince arranged a very successful rat-trap which killed the rat by short-circuiting between two electric wires. Such a trap placed in a rat runway gave no notice to the rat whatever, and always killed him. But it requires some skill to manipulate such a trap, and our Jamaican darkies were so often shocked in trying to arrange it that Mr. Le Prince gave it up.