[PLATE I--A WORKING SET OF THE AUTHOR'S ENDOSCOPIC TUBES FOR LARYNGOSCOPY, BRONCHOSCOPY, ESOPHAGOSCOPY, AND GASTROSCOPY: A, Adult's laryngoscope; B, child's laryngoscope; C, anterior commissure laryngoscope; D, esophageal speculum, child's size; E, esophageal speculum, adult's size; F, bronchoscope, infant's size, 4 mm. X 30 cm.; G, bronchoscope, child's size, 5 mm. X 30 cm.; H, aspirating bronchoscope for adults, 7 mm. X 40 cm.; I, bronchoscope, adolescent's size, 7 mm. x 40 cm., used also for the deeper bronchi of adults; J, bronchoscope, adult size, g mm. x 40 cm.; K, child's size esophagoscope, 7 mm. X 45 cm.; L, adult's size esophagoscope, full lumen construction, 9 mm. x 45 cm.; M, adult's size gastroscope. C, I, and E are also hypopharyngoscopes. C is an excellent esophageal speculum for children, and a longer model is made for adults. If the utmost economy must be practised D, E, and M may be omitted. The balance of the instruments are indispensable if adults and children are to be dealt with. The instruments are made by Charles J. Pilling & Sons, Philadelphia.] [52] CHAPTER II--ANATOMY OF LARYNX, TRACHEA, BRONCHI AND ESOPHAGUS, ENDOSCOPICALLY CONSIDERED The _larynx_ is a cartilaginous box, triangular in cross-section, with the apex of the triangle directed anteriorly. It is readily felt in the neck and is a landmark for the operation of tracheotomy. We are concerned endoscopically with four of its cartilaginous structures: the epiglottis, the two arytenoid cartilages, and the cricoid cartilage. The _epiglottis_, the first landmark in direct laryngoscopy, is a leaf-like projection springing from the anterointernal surface of the larynx and having for its function the directing of the bolus of food into the pyriform sinuses. It does not close the larynx in the trap-door manner formerly taught; a fact easily demonstrated by the simple insertion of the direct laryngoscope and further demonstrated by the absence of dysphagia when the epiglottis is surgically removed, or is destroyed by ulceration. Closure of the larynx is accomplished by the approximation of the ventricular bands, arytenoids and aryepiglottic folds, the latter having a sphincter-like action, and by the raising and tilting of the larynx. The _arytenoids_ form the upper posterior boundary of the larynx and our particular interest in them is directed toward their motility, for the rotation of the arytenoids at the cricoarytenoid articulations determines the movements of the cords and the production of voice. Approximation of the arytenoids is a part of the mechanism of closure of the larynx.