6. Paralysis of the posterior crico-arytenoid muscles, like croup, spasm of the glottis, and all other affections which produce narrowing of the larger air-passages, is distinguished by the dyspnoea being inspiratory, and not expiratory. The function of the posterior crico-arytenoid muscles being to enlarge the glottis, the result of their being paralyzed would be to lessen the opening through which the air passes to reach the lung; and in viewing the cords in such a case with the laryngoscope it will be found that the opening is reduced to a narrow chink. Another distinguishing feature is that the dyspnoea is continuous, and, unlike bronchial asthma, does not come on in paroxysms. 7. An affection which, like asthma, comes on in the night during sleep is the condition known as nightmare, and, like the former disease, is characterized by labored breathing. To distinguish it, it is only necessary to awaken the patient, when the immediate cessation of all symptoms will at once remove all doubt as to the nature of the affection. 8. Through carelessness or ignorance intercostal neuralgia has been {200} sometimes mistaken for asthma. Pain along the course of the nerve and the presence of the points douloureux, which Valleix has described as characteristic of neuralgic affections, are sufficient to establish the diagnosis. 9. Embolism of one of the middle or larger branches of the pulmonary artery is also characterized by great embarrassment of respiration, but is not likely to be mistaken for asthma by any one at all familiar with the two affections. The cachectic appearance of the patient, the intense anxiety depicted on his countenance, the evidence of cardiac disease or of some affection of the vessels, the weakened cardiac impulse, the thready and at times irregular pulse, together with evidences of more or less pulmonary oedema, are sufficient to distinguish this form of dyspnoea from that of asthma. PROGNOSIS.--As there is no well-authenticated case of death from uncomplicated asthma, the prognosis quoad vitam may be regarded as absolutely favorable. That death never occurs during the severe paroxysms of asthma may be due to the action of the deficiently aërated blood upon the respiratory centres, and bronchial spasm, causing relaxation when the symptoms have become most threatening. The asthmatic, if his case be incurable, may live for a number of years, and even attain to extreme old age, but his life will be one of intense suffering, which becomes more intolerable as he advances in years. Sooner or later, bronchitis, emphysema, or heart disease is developed, which in its turn may lead to renal disease and dropsy.