To Villemin, a French physician, belongs the immortal fame of being the first to show the essential distinction in tuberculosis between the virus causing the disease and the lesion produced by it. By inoculating animals, he demonstrated that tuberculosis is a specific disease caused by a specific agent. His paper presented in 1865 before the Academy of Medicine in France contained a detailed account of his experimental investigations. This was a most remarkable contribution to scientific medicine. It remained for Robert Koch in 1882, after years of painstaking investigation, to announce to the world the discovery of a definite bacillus as the causative agent in all forms of tuberculous lesions. Koch isolated, cultivated outside the body, described and differentiated the infective organism of tuberculosis and proved that it could continue to produce the same lesions indefinitely. He showed the presence of the bacilli in all known tuberculous lesions and in tuberculous expectoration, and demonstrated the virulence in sputum which had been dried for eight weeks. Following directly upon the knowledge of the cause of tuberculosis came the recognition of its curability, and the proper means of its prevention. Although good food and fresh air have always been considered of importance in the treatment of the disease, it was not until the middle of the nineteenth century that anything like systematic treatment was undertaken. Dr. George Bodingon of Sutton Coldfield, England, wrote an essay in 1840 advocating fresh air treatment. He denounced the common hospital in large towns as a most unfit place for consumptive patients, and established a home for their care, but met with so much opposition that it was soon closed. In 1856, Hermann Brehmer wrote a thesis on the subject which has been the foundation of our modern treatment. He opened a small sanatorium in 1864. Five years later he established the sanatorium at Goerbersdorf, in Silesia, which eventually became the largest in the world. He advocated life in the open air, abundant dietary and constant medical supervision. He believed that the heart of the large majority of consumptives is small and undeveloped, and that this predisposes them to the disease. In accordance with this theory he put a great deal of emphasis on exercise in the treatment of his patients. He built walks of various grades on the grounds of his sanatorium and installed a system of walking exercise. Patients began with the lowest grade, gradually accustoming themselves to ascend to the highest. Brehmer was himself a consumptive, and was cured by the method he so firmly believed in.