The nerves of the larynx are derived from the superior and inferior laryngeal branches of the pneumogastric or vagus nerve. The superior branch is for the most part sensory (being mainly distributed to the mucous membrane), while the inferior branch communicates motor-power to all the intrinsic muscles except the crieo-thyroid In the preceding account of the cartilages, vocal cords, mucous membrane, inuselcr„ and nerves of the larynx, we have included only the most essential points. For details regarding the attachments of muscles, etc., the reader must consult any standard work on anatomy. That the larynx is the organ of voice, is proved by numerous facts, amongst sehich the following may be mentioned: "First, the least alteration in the con dition of the mucous membrane covering the vocal cords is invariably accompanied by a change in the tone of the voice, e.g., hoarseness; secondly, ulcerative dhease, eating through one or both of these vocal cords, destroys or greatly impairs the voice; thirdly, opening the trachea below the vocal cords, so as to divert the current of air in expiration from the larynx, will destroy the voice; fourthly, section of the inferior laryngeal nerves, by which the influence of the will is brought to bear on the muscles which regulate the tension of the vocal cords, destroys the voice; and lastly, by experiments on the dead larynx, sounds may be produced resembling those of the voice."—Todd and Bowman's
Physiological Anatomy, vol. ii. p. 431.
Diseases of the Larynx.—Of these, the most serious is acute inflammation of the larynx, or laryngitis (q.v.).
Ohldema, or swelling of the glottis, although of common occurrence in laryngitis, may be developed independently of inflammation, from obstruction of the veins leading from that part. or from other causes. The symptoms are those of acute inflammation, except that there is no fever or inflammation, and less difficulty of swallowing. Trach eotomy (the operation of making an opening into the windpipe, below the seat of the disease) affords the patient almost his only chance of life.
Chronic inflammation and ulceration of the larynx are very common in tubercular consumption and in secondary syphilis. In these cases. the laryngeal affection is merely .a local manifestation of a general disease. The chronic hoarseness and cough are often remarkably relieved, in these cases, by swabbing the epiglottis and upper part of the air passages with a strong solution of lunar caustic.