574 THE TISSUES. 



to -g-J-Bv f an i nc h broad, on the average, with elongated round 

 nuclei, and occasionally a few fat-granules. The cilia are fine 

 transparent processes of the cell-membrane, 5 oVo to sitr of an inch 

 long, rising in a broader basis and terminating in a pointed extre- 

 mity. They have been described on page 243; their motion some- 

 times continuing 72 hours after death. It should be, however, re- 

 marked that the epithelium on the vocal cords is a scaly, and not a 

 conoidal ciliated one ; as discovered by H. Rheiner. 



The mucous membrane of the larynx also contains a large num- 

 ber of minute racemose glands (^^ to 2 \ of an inch), like those of 

 the mouth, pharynx, &c., with ca3ca lined by a scaly, and ducts by 

 a conoidal, epithelium. They occur sparsely on the posterior sur- 

 face of the epiglottis. At the entrance of the larynx in front of 

 the arytenoid cartilages, they form a large mass, a horizontal por- 

 tion of which envelops the cartilage of Wrisberg, while another 

 dips down into the laryngeal cavity. Glands also abound in the 

 external wall of the ventricles of the larynx, behind and above the 

 sacciform ligaments. All these glands secrete pure mucus. 



The bloodvessels of the larynx are numerous, but require no spe- 

 cial description. The numerous lymphatics are received by the 

 deep cervical glands. Of the nerves, the more sensitive superior 

 laryngeal contains more fine fibres; while the inferior laryngeal has 

 more thick fibres. (Bidder, VokJcmann). They terminate in the 

 muscles, the perichondrium, and especially in the mucous mem- 

 brane. The branches going to the epiglottis are furnished with mi- 

 croscopic ganglia. 



3. The trachea contains a series of rings of true cartilage, each 

 completing about of a circle ; and between their separated extre- 

 mities is a transverse layer of smooth muscular fibres. On the 

 outer aspect of this, are isolated longitudinal muscular fasciculi, 

 rising by minute tendons of elastic tissue partly from the inner 

 surface of the ends of the tracheal rings, and partly from the ex- 

 ternal fibrous membrane ; which covers the cartilages as a perichon- 

 drium, and at the same time the muscular layer, and connects the 

 different cartilages together. 



The mucous membrane of the trachea has a layer of close areolar 

 tissue, T ^j of an inch thick beneath it, and its corium consists of 

 two layers : 1, an external, of areolar tissue, T i^ of an inch thick, 

 and, 2, an internal, yellow, -fa to yj^ of an inch thick, almost en- 

 tirely composed of longitudinal elastic fibres. The epithelium is 



