Another most important result of the discovery of the cholera bacillus is its use in diagnosis. For example, if a case of suspected cholera is landed at a British port, the sanitary authority at once takes steps to ascertain whether the specific microbe is present; and, according to the answer given by bacteriology, either allows the patient to proceed on his journey, or adopts measures of isolation to prevent the spread of the disease to others. Thus, thanks to the insular position of Great Britain, this dreadful disease has for many years been prevented from invading her population. VIII PLAGUE The _bacillus pestis_ was discovered by Kitasato and Yersin, working independently, in 1894. Yersin's discovery was made at Hong Kong, whither the French Government had sent him to study plague: an excellent account of his work is given in the _Annales de l'Institut Pasteur_, September 1894. The first experiments in preventive inoculation, in animals, were made by Yersin, Calmette, and Borrel, working conjointly, in 1895. They found that it was possible to confer on animals a certain degree of immunity, by the hypodermic injection of dead cultures of the bacillus. These experiments were made on rabbits and guinea-pigs. Haffkine's fluid was first used on man in January 1897. It is a _bouillon_ containing no living bacilli, and nothing offensive to the religious beliefs of India.[33] He proved its efficacy on rabbits; and then, on 10th January 1897, inoculated himself with a large dose, four times as strong as the subsequent standard dose. A few days later, Lieut.-Col. Hatch, Principal of the Grant Medical College, Bombay, and other members of the College Staff, were inoculated. These first inoculations were described by Haffkine in a lecture (1901) at Poona:-- "In a short time, a number of the most authoritative physicians in Bombay, European and native, official medical officers and private practitioners, submitted themselves for inoculation. It is a matter of gratification to me to be able to quote, among these authorities, the Head of the Medical Service of the Presidency, Surgeon-General Bainbridge, who not only got himself inoculated, but inoculated also the members of his family. Previous to that, Surgeon-General Harvey, the able Director-General of the Indian Medical Service, submitted himself to inoculation in 1893 against cholera; and, in 1898, against plague. It was the example of these gentlemen, whose competence in the matter of health could not be disputed, that encouraged thousands of people, rich and poor, in Bombay and elsewhere, to come forward for inoculation. Thus his Excellency the Viceroy thought it right to tell you here, in Poona, that previous to his starting for the plague-stricken districts he and his staff had also undergone the prophylactic inoculation. In due course, mothers brought their children to be protected by the new 'vaccination.'"