LAEYNGITIS. 305 



and aids in the obstruction of the airway. The position of the 

 funnel-shaped aperture of the Eustachian tubes on the lateral 

 walls of the naso-pharynx explains the frequency of the extension 

 of inflammation to the mucous membrane lining the tubes. 

 Normally the cilia of the epithelium covering the membrane 

 work towards the naso-pharynx, carrying secretions away from 

 the tympanum and preventing the entrance of bacteria into that 

 cavity. 



The interference with nasal respiration caused by adenoid 

 vegetations produces typical, and not infrequently serious, 

 deformities. The nostrils and the nasal cavities may continue 

 small and ill-developed from want of full use, and the arch of 

 the palate remains higher than normal, with a tendency to 

 crowding, and frequently misplacement, of the incisor teeth. 

 The thoracic walls, from insufficient expansion, become con- 

 siderably altered in shape, and exhibit a characteristic circular 

 depression at the junction of the lower and middle thirds from 

 the traction of the diaphragm and atmospheric pressure, whilst 

 the upper part of the cavity seems to be abnormally enlarged. 



LARYNX. 



Congenital malformations of the larynx are rare, but the 

 exaggeration of the normal peculiarities of the infantile larynx 

 is the basis of the condition known as congenital laryngeal 

 stridor. In these cases the epiglottis is much folded on itself 

 vertically and the aryteno-epiglottidean folds are closely approxi- 

 mated. During inspiration the sides of the laryngeal aperture 

 tend to be sucked inwards, and obstruction with a stridulous crow 

 results. 



Catarrhal Laryngitis. The larynx, owing to its proximity to 

 the nose, mouth and pharynx, is exposed to air-borne infection, 

 to the action of irritant vapours, and to injury during the swallow- 

 ing of corrosive fluids or rough solid bodies. The continuity of 

 its mucous membrane with that of the fauces explains the spread 

 of inflammation from the nose or throat. The laryngeal mucous 



C.A.A. 20 



