APHONIA, or loss of voice, is a symptom of disease of the larynx or interference with the nervous mechanism which controls its muscles. Of causes in the larynx itself, the commonest is acute catarrhal laryngitis, in the course of a cold, or of ter over use of the voice. More serious diseases of the larynx are diph theria, tuberculosis, syphilis, and cancer, each of which may pro duce hoarseness or loss of voice when it attacks the vocal cords. Causes outside the larynx are masses pressing on the laryngeal nerves, such as tumours of the thyroid gland and aneurisms of the aorta, and disorders in the brain giving rise to spasm or paralysis of the laryngeal muscles. Aphonia may be a manifestation of hysteria.