37$ EPITHELIUM AND GLANDULES. [sect. 1 73. 



them. The cilia are more delicate than the cell-membranes, and 

 very readily fall off on slight maceration of the epithelium. They 

 are more or less altered by almost all re-agents, and by many are 

 immediately destroyed; chromic acid, however, does not affect 

 them much. When they have ceased to play, they may again be 

 made to move actively for a while (as Virchow discovered) by the 

 addition of diluted caustic potass or soda. In man, the ciliary 

 movement proceeds, in the trachea, from below upwards, and is 

 often perceptible fifty-two or even seventy-eight hours after death 

 {Bicrmer, Gosselln). Desquamation of the ciliated epithelium of 

 the larynx and air-passages is never presented normally. Separate 

 ciliated cells, it is true, are occasionally detached, and discharged 

 externally with the mucus of the air-tubes; but no traces of a 

 more extensive detachment of the ciliated cells are met with. 

 Even in diseases of the respiratory passages, the falling-off of the 

 ciliated cells is by no means such a usual phenomenon as is 

 believed by many, and the epithelium may frequently be found 

 after death more or less uninjured amongst puriform mucus, and 

 even in the midst of croupous exudation. The manner in which 

 the fallen -off ciliated cylinders are replaced is, perhaps, simply by 

 the multiplication of the deeper cells (by a process of partition of 

 the cell), which move towards the surface, while cilia are repro- 

 duced on the most external. Probably, also, in desquamation the 

 long cylinders may divide transversely, and new cilia may form on 

 the surface so exposed, an opinion which receives confirmation 

 from the observation of Valentin and Biermer, that many of these 

 cylinders have two or three nuclei one behind the other. 



The mucous membrane of the larynx contains a considerable 

 number of small glands, which are all of the racemose kind. Like 

 those of the oral cavity, of the pharynx, etc., they possess roundish 

 gland-vesicles, of o , 03'" to o'o^" in diameter, with a pavement- 

 epithelium, and excretory ducts with cylindrical cells. Some of these 

 glandules lie scattered upon the posterior surface of the epiglottis, 

 where they are frequently imbedded in depressions of the cartilage, 

 and in the cavity of the larynx itself, where their openings, the 

 size of pins' heads, are readily visible to the naked eye. In these 

 situations, their size is from -^'" to J'" in diameter. Others of 

 these racemose glandules form a large cluster at the entrance of 

 the larynx, in front of the arytenoid cartilages, and a horizontal 

 process from this cluster envelopes the cartilage of Wrisberg, while 

 another portion descends into the cavity of the larynx (glandida 

 arytcenoidea laterales). Glandules also lie upon the arytcenoideus 



