ETIOLOGY.--In addition to the general causes of laryngeal paralysis, the use of the voice in an unnatural or too high a key or the too long-continued use of the organ may result in a temporary or even permanent impairment of the power of these muscles. Their exposure to the causes of inflammation, lying as they do so near the surface of the mucous membranes, subjects them to the morbid influences of the catarrhal troubles to which the glottis is liable. They are probably more frequently affected than the literature of the subject would lead us to suppose, as in many cases the disease is temporary. SYMPTOMS.--These consist mainly in the alteration of the voice. It is hoarse, the register is lower, the quality is uneven. Occasionally a note is, if not lost, uttered with difficulty; some letters, such as the aspirates, requiring the careful adjustment of the glottis, are articulated with great uncertainty. There is what has been called a rattling of the voice. It is quite impossible to sing or to speak long in a high key; even prolonged ordinary conversation gives rise to fatigue, for the reason that there is so great a waste of air in the effort. The pressure upon the under surface of the cords in their relaxed condition forces its way upward and through the glottis without throwing them into normal vibration. DIAGNOSIS.--The laryngeal mirror reveals the glottis only partly closed. There is an oblong opening extending from the thyroids to the base of the arytenoid cartilages. The vocal processes even are not brought to the median line, but are so far apart as to leave a noticeable slit between them. It seems from this fact that these muscles are therefore the aids of the lateral {86} crico-arytenoids in the rotation of the cartilages on their bases. In the effort at phonation the cords are seen to move with difficulty. The disease may be unilateral or bilateral. This form of paralysis in course and termination does not in any essential respect differ from other paralyses of the larynx. The duration is therefore very uncertain, and will depend largely upon the cause of the affection. Paralysis of the External Tensors of the Cords. This is a rare disease, but is present in complete paralysis of the superior laryngeal nerve. It is then associated with anæsthesia of the superior portion of the glottis, as well as paresis of the depressors of the epiglottis, and generally of the constrictors of the vestibule of the larynx. ETIOLOGY.--It may be the result of injury to the external branch of the superior laryngeal in its distribution to the muscles. It may be caused by diphtheria. It is possible that the motor fibres of the superior laryngeal nerve may be alone involved, while the sensitive portion is still normal. Cases of partial paralysis are recorded by Von Ziemssen, Gerhardt, and others.