Page:The Harveian oration - delivered at the Royal College of Physicians, October 18th, 1899 (IA b24975941).pdf/27

 century has been the discovery of microscopic parasites in the blood and tissues. It is but fifty years since Davaine demonstrated the Bacillus anthracis in the blood, and the facts of a similar order since accumulated have bewildered us by their number and varicty. To take only one example, we have attained to a certain knowledge of the physical cause of the plague, which in times past has numbered its victims by hundreds of millions. This discase has been isolated and cultivated. It has been sent half round the world in a tube, and has been re-inoculated in animals. Some of these animals accidentally transmitted the disease to their keeper, who, in his turn, infected his medical atten- dant and nurses. The disease manifested all its ancient virulence, but a knowledge of the cause enabled the plague to be staid. The much honoured and lamented victims of Vienna have demonstrated to the world at large how the pestilence which walketh in darkness has been illuminated by the full light of science.

We are full of hope as to the good which will follow on the discovery of the malaria parasites in the blood, and their transference by means of mosquitos. The part which insects play in the causa- tion of the diseases of mon and animals is proving to be a fertile field of research, and it is not impossible that those who are called upon to take up the white man's burden in the tropies may learn to