1. Microscopical examination of sputum that has been washed with isotonic salt solution indicates its source. Sputum from above the vocal cords contains polygonal flat epithelial cells and numerous species of non-pathogenic microorganisms. Sputum from below the cords is clear of saprophytes, although it sometimes contains bronchoalveolar cuboidal cells.
2. The source of the sputum can be determined by the erythrocytes and the bacilli that are contained in it, and the site of the lesion can also be ascertained.
3. In every instance I found erythrocytes in the pulmonary sputum after severe pulmonary hemorrhage.
4. Six of the cases of laryngeal affection referred to in the presentpaper had had no subjective symptoms, but microscopical examination showed tubercle bacilli in the laryngeal sputum. All the six cases were examined by Dr. Tanaka and were found to have tuberculous lesions in the larynx. In the laryngeal sputum of most cases of laryngeal tuberculosis with symptoms, tubercle bacilli have been frequently demonstrated, while in some cases contaminated laryngeal sputum was obtained only after a long series of examinations.
5. Microscopical examination of the sputum plays a significant part in the diagnosis of tuberculosis.