4. Spasm of the glottis, croup, oedema of the glottis, tracheal stenosis, are all attended with more or less violent attacks of dyspnoea. We are indebted to Biermer for having directed attention to an important symptom by means of which all these affections may be distinguished from bronchial asthma. In the latter, and in all other diseases causing narrowing or obstruction of the finer bronchi, the dyspnoea is during the expiration, but if the impediment be in the larger air-passages the dyspnoea will be during the inspiration. "Dyspnoea during expiration is just as characteristic of narrowing of the finer bronchi as the same condition during inspiration is of croup and other forms of laryngeal stenosis." In croup the neck is extended and the head thrown back. Notwithstanding the violent inspiratory efforts of the patient, the lungs are but partially filled; the air in them becomes rarefied, causing a yielding of the less-resisting parts of the thorax--_e.g._ the supraclavicular space, the lower portion of the sternum, and adjacent costal cartilages--and a sinking in of the abdomen. During expiration, which is accomplished quickly and with comparative ease, the thorax resumes its natural form. In bronchial asthma, on the contrary, the head is thrown forward, and the shoulders fixed in such a position as to enable the muscles of expiration to work to the best advantage. The thorax, instead of sinking in, is expanded and abnormally round, giving on percussion the peculiar pasteboard-box sound (Schachtelton) which Biermer has described as characteristic of inflation of the alveolæ. In croup the sibilant râles are heard during inspiration, while in asthma they are more pronounced during expiration. 5. Spasm of the diaphragm is another affection from which it may be necessary to distinguish bronchial asthma. This rare disease, which is almost always associated with hysteria, is characterized by a short inspiratory movement, during which all the muscles of inspiration are brought into action, and we have the same sinking in of the more yielding portions of the thorax which has just been mentioned as one of the distinguishing features of laryngeal stenosis. After this the thorax remains fixed for a few seconds, the muscles of inspiration remaining in a state of contraction. There then ensues a quick and powerful expiratory effort, accompanied by a sound not unlike that of hiccough; then another inspiration, with a repetition of the above symptom; and so on until the attack is over. It will be seen from this description that this affection resembles singultus more than asthma, and that there is but little likelihood of its being mistaken for the latter disease.