I think I have here shewn, that by means of the stethoscope,[13] I obtained much extent, and the progress of the inflammatory symptoms; and that I was thereby enabled to direct my local treatment with greater accuracy and advantage, than I could have done, if confined to the ordinary modes of investigation. The cases which I have here related, correspond with Laennec’s description of acute pulmonary catarrh, or bronchitis, a term which I have been accustomed to consider, more applicable to the inflammation affecting the larger branches of the bronchia proceeding immediately from the trachea. When the ramifications extending through the lung are inflamed, it constitutes a case, either mixed with, or, so much resembling genuine pneumonia or inflammation of the substance of the lungs, that, in a practical point of view, the distinction does not perhaps appear important; but yet, accuracy of diagnosis should always be desired. In the case of a young gentleman lately under my care, the symptoms of inflammation in the lungs were acute, of considerable continuance, and apparently distinct from any affection of the bronchia, as the stethoscope did not afford the sonorous rattle, but only the crepitating and mucous kinds. I do not speak of this as a solitary example which has occurred to me. At this moment I am attending an elderly gentleman severely ill with pneumonia; and, in examining his chest, I cannot discover the sonorous rattle except in one small point; but I meet with other phenomena, as the crepitating rattle in one part, and the indication of obstruction of the air cells in another. I take this occasion to observe, that in my study of the volumes of Laennec and Forbes, I do not discover so much mention as my experience would have led me to expect, of the strong sonorous rattle, or sharp tones (which in their variety admit of almost endless comparisons), as being characteristic of the existence of more or less active inflammation of the bronchia. I have found this species of rattle serve, in a remarkable manner, to point out the exact seat of the inflammatory action; and in proof that I have not been drawn into false conclusions from these particular indications of the stethoscope, I have been successful in my treatment, and have ceased to perceive the tones, in the same proportion as the inflammation has passed away. Laennec, when speaking of the sonorous rattle, observes, “I am led by my dissections to believe that it is produced by the partial obstruction or narrowing of part of the tract of a bronchial tube, whether this takes place from the pressure of a tumour, or of a portion of the lung condensed by inflammation, or by the obstruction produced by a portion of tenacious mucus, or by the partial thickening of the internal coat of a bronchial ramification.”