Mental emotion, if sufficiently powerful, may sometimes prevent the occurrence of the asthmatic paroxysm; thus, Steavenson, referring to his own case, states that although subject to frequent attacks he never had one on going up for an examination; and the writer is acquainted with a patient whose attack of hay asthma could frequently be checked by an exciting game of cards. Asthma, like other neuroses, is much more frequent among the educated and refined than among the coarser and more ignorant classes of society, and those leading luxurious lives are more liable to the disease than those of simple and frugal habits. Of the various professions, those which involve much exertion of the voice furnish the largest contingent; hence it is common among public speakers, clergymen, and lawyers. In former days the retrocession of cutaneous eruptions was supposed to play an important rôle in the production of asthma, but of late years this theory of causation has found but few advocates among intelligent physicians, the only author of any prominence who still adheres to it being Waldenburg, who has proposed to designate such cases as a. herpeticum. PATHOLOGY.--We have elsewhere alluded to the various theories with which the older writers endeavored to explain the phenomena of asthma, and need not here refer to them again. The first step toward a truly scientific theory of the pathology of asthma was the discovery by Reisseisen of the smooth muscular fibres of the bronchial tubes. These fibres are found not only in the large and medium-sized bronchi, but even in those of the smallest calibre, Kölliker having {194} demonstrated them in bronchioles 0.18 millimeter in diameter. It was ascertained by Williams that by irritating the lung he could cause contraction of these fibres, and Longet subsequently proved that the same effect could be produced by galvanizing the pneumogastric nerve. Guided by these important discoveries, most modern pathologists have arrived at the conclusion that bronchial asthma is a spasmodic contraction of the middle and finer bronchi, dependent upon some derangement in the function of the pneumogastric nerve. This, the so-called spasmodic theory, is not entirely new, Willis, as we have before stated, having described as early as 1682 a variety of asthma which he believed to be the result of a "spasmodic action of the muscles and nerves of respiration," and to which he applied the term "asthma convulsivum." Although revived from time to time, it was not until some two hundred years later, and after Romberg had definitely settled the question of the essential character of the disease, that the spasmodic nature of asthma received general recognition. Bergson adopted it in his prize essay in 1840, and ten years later it found a warm supporter in the person of Hyde Salter, whose valuable contributions have added so much to our knowledge of bronchial asthma. The theory that asthma is due to spasm of the bronchial muscles met