572 SPECIAL HISTOLOGY. 



glandules, all of which belong to the category of minute racemose glands ; 

 and, like those of the oral cavity, pliarynx, &c., present rounded gland- 

 vesicles of 0-003-0-04 of a line with a tessellated epithelium, and excre- 

 tory ducts lined Avith a cylinder-epithelium. They are situated, in part 

 scattered as minute glandules of yVs o^ ^ ^'^i®? o" ^^® posterior surface 

 of the epiglottis, where they are frequently imbedded in depressions, 

 which may even perforate the cartilage, and in the cavity of the 

 larynx itself, where their arifices, such as might be produced by a 

 needle, are easily seen ; in part they occur at the entrance of the 

 larynx, in front of the arytenoid cartilages, forming a large aggre- 

 gate mass, a horizontal division of which envelops the cartilage of 

 Wrisberg, whilst a second dips down into the cavity of the larynx 

 [glandulce arytcenoidece laterales). Glandules are also placed upon 

 the arytcenoideus transversus and a considerable mass of them pre- 

 sents itself externally, in the ventricles of Morgagni, behind and 

 above the sacciform ligaments. The secretion of these glands, as of the 

 oral glands, is pure mucus, without any morphological elements. 



The larynx is richly supplied with vessels and nerves. The former, 

 in the mucous membrane, present the same conditions as in the pharynx 

 and ultimately breaking up into capillaries, 0-003-0-004 of a line, form 

 a superficial plexus. The lymphatics arc numerous and are received by 

 the deep cervical glands. Of the nerves, we^learn from Bidder-Volck- 

 mann, that the more sensitive laryngeus superior contains a prepon- 

 derance of fine fibres, whilst the inferior, whose properties are more of 

 a motor nature, has more thick fibres. They terminate in the muscles, 

 the perichondrium and, especially, in the mucous membrane, in which 

 they are disposed as in the pharynx; the branches going to the epi- 

 glottis are also furnished with microscopic ganglia. 



The glands of the larynx and of the air-passages are frequently 

 altered in catarrh, so that their vesicles measure as much as 0-08, or 

 even 0-15 of a line, and are filled with minute, rounded cells, which may 

 probably be compared with the mucous corpuscles formed on the sur- 

 faces of mucous membranes. 



§ 174. The trachea and its branches are united to the contiguous 

 parts by a connective tissue abounding in well-defined elastic fibres ; 

 they are then surrounded by a tough, elastic, fibrous tissue, which 

 covers the cartilaginous rings, like a perichondrium, connects them 

 together, and, in a somewhat thinner layer, invests the posterior mem- 

 branous wall of the canal in question. To this layer succeed the carti- 

 lages, in front and on the sides, while posteriorly there is a layer of 

 smooth muscles. The former, ^-h a line thick, are constituted ex- 

 actly like the larger cartilages of the larynx, but exhibit no tendency 

 to become ossified. The muscles, on the contrary, from the trachea 

 onwards, cease to be of the striped kind and constitute, on the pos- 



