THE LUNGS. 569 



trachea, and larynx, constitute the excretory apparatus. They differ 

 from common glands in this, that since in the lungs a double process 

 an excretion and an absorption of matters is carried on, which affects 

 the whole mass of blood, the cavities are proportionately more capa- 

 cious, and also, on account of the special nature of their contents, of a 

 peculiarly compact, and, at the same time, elastic structure. 



173. The larynx is the most complex portion of what are termed the 

 air-passages, and consists, in the first place, of a firm framework, the 

 cartilages of the larynx, together with their ligaments; secondly, of nu- 

 merous small muscles attached to them ; and lastly, of a mucous mem- 

 Irane, abounding in glands, with which they are lined. 



The cartilages of the larynx are not all alike in their structure, some 

 being composed of common cartilaginous tissue, others of fibro-c&rtilage, 

 whilst others, again, are constituted of the so-termed reticular or yellow 

 cartilage. To the former belong the thyroid-, cricoid-, and arytenoid- 

 cartilagcs ; all of which present a more homogeneous, hyaline matrix, 

 with scattered cartilage cells imbedded in it (Fig. 20), and approach 

 nearest to the costal among the other true cartilages. Most externally 

 they contain flattened cells, to which succeeds a whitish layer, with nu- 

 merous large parent-cells and a more fibrous fundamental substance ; 

 and, lastly, in the interior, a larger proportion of matrix and minute 

 radiating cavities. The membranes of the cells are thickened, and, in 

 their interior, a large oil-drop is most usually found. Incrustations of 

 the cartilage-cells and of the matrix, with minute calcareous granules, 

 are very frequent in the laryngeal cartilages ; but besides these, true 

 ossifications occur, which are always attended with the formation of 

 larger cavities, filled with a well-marked, gelatinifortn, vascular medulla. 

 The epiglottis and the cartilages of Santorini and of Wrisberg, consist 

 of ydlow or reticular cartilage (vide 22, Fig. 21), presenting opaque, 

 very closely interlaced fibres, which, in animals (e. g. the Ox), are much 

 thicker than in Man, and clear cells, 0-01-0-02 of a line in size, in which 

 Henle, in one instance, noticed a concentric disposition of such a kind 

 that the remaining cavity of the cell resembled a simple bone-lacuna 

 with a few prolongations (Allg. Anat., Tab. V., Fig. 8). The cartilage 

 triticea consists of connective tissue with scattered cartilage-cells, and 

 is, consequently, common fbro-cartilage. 



Of the ligaments of the larynx, the ligg. crico-thyreoideum medium 

 and thyreo-arytcenoidea inferior a contain a preponderance of elastic tissue 

 and are of a yellow color : whilst others, such as the thyreo-arytwnoidea 

 superiora, hyo- and thyreo-epiglottica, and the membr. hyo-thyreoidea, 

 are characterized, at all events, by the great abundanceof that element 

 which they present. The elastic fibres of the laryngeal ligaments are 

 of the finer sort, scarcely exceeding O'OOl of a line, and are united in 



