DIAGNOSIS.--The principal diseases from which acute inflammation of any part of the bronchial mucous membrane needs to be differentiated are pneumonia, pleurisy, laryngitis, tracheitis, and asthma, while it is still more important to keep a clear line of diagnosis between the chronic grades of bronchial inflammation and the earlier stages of pulmonary phthisis and of emphysema. From nearly all the diseases named it is separated by negative evidence or the absence of symptoms and physical signs characteristic of those affections. It neither presents the rusty expectoration or high temperature or fine crepitant râle of pneumonia, nor the acute pains or short stifled cough or friction-sounds of pleurisy in the early stage, and still less is there in the middle and later stages any of the dulness on percussion that characterizes the corresponding stages of the other two diseases. In true asthma the active symptoms are distinctly paroxysmal, without fever or increase of temperature, and the respiration during the paroxysms is slow, with marked prolongation of the expiratory act; while in bronchitis, both catarrhal and capillary, the symptoms are continuous, the temperature increased, and the respirations more frequent than natural. All grades of bronchitis are easily distinguished from laryngitis and tracheitis by auscultation, which enables us {177} to trace all the morbid sounds to the chest in the former, and to the front part of the neck in the two latter. The great advantage of recognizing pulmonary tuberculosis and other forms of phthisis in the early stage of the disease makes the diagnosis between it and chronic bronchitis a matter of primary importance. This can be readily done by all practitioners who have acquired a reasonable degree of skill in the practice of auscultation and percussion. In all forms and stages of pulmonary phthisis, whether from primary tubercular deposits, pneumonic exudation followed by caseous degeneration, or from interstitial fibroid sclerosis, there is increased vocal fremitus and diminished resonance on percussion; neither of which is present in any grade of uncomplicated bronchitis. It is true that in the advanced stage of some very severe cases of capillary bronchitis there occurs sufficient pulmonary oedema to increase the vocal fremitus and diminish the resonance over some parts of the chest; but the accompanying symptoms and immediately preceding history of such cases are sufficient to separate them from any stage of phthisis. The same remark is applicable to those rare cases in which an attack of pseudo-membranous bronchitis results in the complete occlusion of one or more of the bronchi and the permanent collapse of the pulmonary lobules to which the occluded tubes lead. If in addition to the plain difference in the physical signs already mentioned we remember that in all the forms of phthisis there is progressive loss of flesh, some increase of