We have already spoken of hypertrophy of the mucous membrane of the air-passages, of the muscular fasciculi of the trachea, of the fibrous sheaths of the bronchial tubes in cases of dilatation arising from catarrh and blennorrhcea, and of hypertrophy of the mucous follicles in the posterior wall of the trachea, when that canal is the seat of dilatation; it now remains for us to consider more especially hypertrophy of the mucous membrane and of its follicles in the larynx and the trachea.

When only moderately developed it presents the ordinary characters of hypertrophy of mucous membranes. In a higher degree it especially affects the mucous glands, and in the larynx gives rise to glandular swelling of the mucous membrane at those points where the glands are most abundant, as for instance, on the superior vocal chords,- in the ventricles, over the transverse muscle, and on the epiglottis. In the trachea we observe, in the swollen mucous membrane of the posterior tracheal wall, the dilated mouths of the excretory ducts of mucous glands, lying behind the muscular layer. These glands enlarge to the size of a hemp-seed, or even to that of a pea or cherry, and become converted into simple, or sinuous, imperfectly partitioned sacs, in whose cavities there is an accumulation of a whitish, opaque, or transparent and vitreous mucus. In its highest degree the glandular swelling of the laryngeal mucous membrane degenerates into polypoid hypertrophy, or into cellular or mucous polypi.

Atrophy exhibits itself in the form of a wasting of the mucous membrane and glands of the air-passages, especially in the larynx and trachea, a deficiency of mucous secretion, and, at the same time, attenuation of the laryngeal muscles, and is followed by the dilatation of the larynx, trachea, and bronchi which we have already noticed as peculiar to old age. The epiglottis is sometimes the seat of atrophy and relaxation, arising apparently from slow inflammation; or, on the other hand, it may become indurated and variously misshaped, and thus rendered in-. sufficient for its duties. Further, we must here mention the frequent cases of attenuation and final absorption of the laryngeal cartilages, and the tracheal and bronchial rings with their intervening membranes, arising from the pressure of superimposed tumors, and especially of aneurisms.