Half a century has passed since Robert Koch, then working in Egypt, described the vibrio of cholera. The insusceptibility of the common laboratory animals to the disease has made it difficult to furnish as convincing direct experimental demonstrations of the etiologic potency of Vibrio cholerae as has been the case in some of the other infectious diseases. Nevertheless, in the course of time sufficient evidence has accumulated in other ways to leave no doubt today that Koch's vibrio is the specific infective agent in cholera. For prophylactic purposes Ferrau and Haffkine have inoculated more than half a million men with living cultures of the cholera vibrio without causing a single case. Hence the comment that "you can eat cholera, you can drink cholera, but you cannot catch it."
An effort to explain the existing confusion has been made by d'Herelle,1 well known for his pioneer investigation of the bacteriophage,