Richard Morton, an English physician, wrote, in 1689, of the wide prevalence of pulmonary tuberculosis, and recognized the two types of fever: the acute inflammatory at the beginning, and the hectic at the end. He also recognized the contagious nature of the disease and recommended fresh air treatment. He believed the disease curable in the early stages, but warned us of its liability to recur. Morton taught that the tubercle was the pathological evidence of the disease. In 1690, Leeuwenhoek, a Dutch lens maker, started the making of short range glasses which resulted later in the modern microscope, making possible the establishment of the germ theory of disease, including the establishment of that theory for tuberculosis. Starck, whose observations and writings were published in 1785 (fifteen years after his death), gave a more accurate description of tubercles than had ever been given before, and showed how cavities were formed from them. Leopold Auenbrugger introduced into medicine the method of recognizing diseases of the chest by percussion, tapping directly upon the chest with the tips of his fingers. The results of his investigations were published in a pamphlet in 1761. This new practice was ignored at first, but after the work of Auenbrugger was translated he attained a European reputation and a revolution in the knowledge of diseases of the chest followed. Boyle recognized in miliary tubercle, as it was afterwards called by him, the anatomical basis of tuberculosis as a general disease, and, in 1810, published the results of one of the most complete researches in pathology. He described the stages in the development of the disease, using miliary tubercle as its starting point. He opposed the theory that inflammation caused tuberculosis and declared hemorrhage a result and not a cause of consumption. Laennec discovered one of the most important, perhaps, of all methods of medical diagnosis--that of auscultation. By means of the stethoscope, which he invented in 1819, he recognized the physical signs and made the first careful study of the healing of tuberculosis; he gave also one of the best accounts of the sputum of the consumptive. He believed that every manifestation of the disease in man or animals was due to one and the same cause. Up to this time the views which were held concerning the infectious nature of tuberculosis were not based upon direct experiment, but in 1843 Klenke produced artificial tuberculosis by inoculation. He injected tuberculous matter into the jugular vein of a rabbit, and six months later found tuberculosis of the liver and lungs. He did not continue, however, his researches; so they were soon forgotten.