I. DISEASES OF THE RESPIRATORY ORGANS. 1. GENERAL REMARKS ON THE RELATIONS EXISTING BETWEEN THE NOSE, PHARYNX, AND LARYNX. THE upper air-passages, comprising the nose, pharynx, and larynx, present a canal of varying form and diameter, lined in its entire extent, except where the respiratory and alimentary tracts cross each other in the pharynx, by mucous membrane covered with ciliated columnar epithelium; so that nose, pharynx, and larynx imperceptibly merge one into the other without the interposition of a sharp line of demarcation. It follows that pathologic changes in any portion of the upper air-passages are not sharply limited in their local effects and ultimate consequences, but invade adjacent areas quite irrespective of the anatomic boundaries of nose, pharynx, and larynx. It is well known that catarrhal affections of the upper air-passages are not limited to a circumscribed area; they display, on the contrary, a peculiar descending character, as it is called, beginning in the nose as an acute rhinitis and invading at certain definite intervals the pharynx and the larynx. The comparative immunity enjoyed by the larynx as compared to the pharynx is not altogether accidental, although to a certain extent dependent on accidental causes, for it is generally admitted that progressive morbid processes meet with a certain resistance wherever the character of the epithelium changes, which resistance may be sufficient to arrest their further advance. Now, the ciliated columnar epithelium of the nose and nasopharynx is replaced in the oral pharynx by squamous epithelium, which extends as far as the upper border of the larynx; but at this point the epithelium returns to the ciliated columnar type of the higher air-passages, and this type is retained throughout the interior of the larynx-with the exception zone of squamous epithelium extending over the interarytenoid notch to the posterior wall and to the vocal cords. Hence we can readily understand that the boundaries between these various kinds of epithelium oppose to the progress of an acute catarrh a barrier more or less insurmountable, according to the intensity of the process and the disposition of the individual. In the comparatively rare cases where the larynx becomes involved in a descending catarrh, the laryngeal symptoms develop several days after the first appearance of the nasal and pharyngeal symptoms, or even after convalescence has begun in the higher air-passages. Ascending catarrh, on the contrary, differs diametrically from the descending form in the matter of frequency, and it seldom or never happens that an acute pharyngitis or laryngitis spreads to the higher portions of the respiratory tract. With the infectious diseases, especially diphtheria, the case is quite different; they may originate either in the pharynx or in the nose, although, as a matter of fact, they usually appear first in the pharynx, and spread from that region either upward into the nose or downward to the larynx. The relation between the nose and the nasopharynx is a particularly intimate one, so much so that only very few diseases are limited to one or the other of these two structures. Any chronic condition leading to obstruction and to the passage of morbid products—such as mucus and pus-into the nasopharynx exerts an injurious effect on that structure; and, conversely, any disease of the nasopharynx, by causing chronic enlargement of the pharyngeal tonsils, thereby obstructing the nasal passages and interfering with nasal respiration, sets up a congestive catarrh; the secretions accumulate as the expiratory blast is no longer able to remove them, and a hyperplasia of the mucous membrane eventually results. If, on account of obstruction, the nasal secretion is unable to make its escape outward and flows back into the nasopharynx, the harm which results is not confined to this locality; the discharges trickling down along the posterior pharyngeal wall accumulate in the oral pharynx, and the subsequent course of the disease then depends on the quantity and consistency of the morbid secretion. If the patient is unable to remove it by hawking and coughing, it will adhere to the posterior pharyngeal wall in the form of a thick, tenacious coating, and thence will gradually spread to the posterior wall of the larynx. This mode of spreading from the nose to the pharynx and larynx is especially characteristic of certain definite diseases, the most typical of which is atrophic rhinitis with fetor and crust formation. The greenish-yellow, foul-smelling crusts with which the atrophied nasal cavities are covered—as the walls of a room are covered with wall-paper-are also found clinging to the roof and posterior wall of the pharynx, while in the larynx a tenacious material accumulates on those parts which are least concerned in the movements of phonation and respiration, especially in the region below the glottis. Similar consequences attend any chronic inflammation of the nose, accompanied with copious secretion and suppurative processes in the tributary cavities of the nose, whenever the position of their openings permits a backward flow of pus. 2. RELATIONS EXISTING BETWEEN THE NOSE, PHARYNX, LARYNX, AND LUNGS. SIGNIFICANCE OF THE UPPER AIR-PASSAGES IN THE PHYSIOLOGY OF BREATHING. Leaving the description of the interdependence of nose, pharynx, and larynx, which really belongs to the domain of special pathology, we now turn our attention to the influence exerted on the lungs by disease of the upper air-passages. The first requisite for a thorough understanding of this subject is a knowledge of the physiologic significance of the air-passages in the act of respiration. They should not be viewed merely in the light of canals for the transmission of the inspired air; for each segment has a special function of its own and contributes to the preparation of the air for reception in the lungs, and this function can not remain in abeyance without detriment to the organism. We begin with the consideration of the upper air-passages as the respiratory pathway and with the changes experienced by the inspiratory air-current during its passage through the nose. |