With the new technique and experimental methods, the discovery of the specific germs of many of the more important acute infections followed each other with bewildering rapidity: typhoid fever, diphtheria, cholera, tetanus, plague, pneumonia, gonorrhoea and, most important of all, tuberculosis. It is not too much to say that the demonstration by Koch of the "bacillus tuberculosis" (1882) is, in its far-reaching results, one of the most momentous discoveries ever made. Of almost equal value have been the researches upon the protozoan forms of animal life, as causes of disease. As early as 1873, spirilla were demonstrated in relapsing fever. Laveran proved the association of haematozoa with malaria in 1880. In the same year, Griffith Evans discovered trypanosomes in a disease of horses and cattle in India, and the same type of parasite was found in the sleeping sickness. Amoebae were demonstrated in one form of dysentery, and in other tropical diseases protozoa were discovered, so that we were really prepared for the announcement in 1905, by Schaudinn, of the discovery of a protozoan parasite in syphilis. Just fifty years had passed since Pasteur had sent in his paper on "Lactic Acid Fermentation" to the Lille Scientific Society--half a century in which more had been done to determine the true nature of disease than in all the time that had passed since Hippocrates. Celsus makes the oft-quoted remark that to determine the cause of a disease often leads to the remedy,(*) and it is the possibility of removing the cause that gives such importance to the new researches on disease. (*) "Et causae quoque estimatio saepe morbum solvit," Celsus, Lib. I, Prefatio.--Ed. INTERNAL SECRETIONS