190 



NORMAL HISTOLOGY. 



The nerves supplying the larynx are chiefly from the vagi, intermingled 

 with fibres from the sympathetic. They consist, therefore, of medullated and 

 nonmedullated fibres, groups of ganglion-cells occurring along the course of 

 the sympathetic fibres. The latter are destined for the blood-vessels and 

 glandular tissue. The muscles being of the striated variety are supplied by 

 fibres bearing motor end-plates. The sensory fibres are distributed princi- 

 pally to the mucous membrane, in which they form plexuses. From the latter 

 nonmedullated fibres pass towards the free surface to terminate either in sub- 

 epithelial end-arborizations, bearing enlargements or end-bulbs,' or in intra- 

 epithelial filaments ending free between the cells. Special end-organs 

 have been described as existing within the true vocal cords. 



THE TRACHEA AND BRONCHI. 



Beginning at the lower border of the cricoid cartilage, the trachea or 

 windpipe extends into the thorax, a distance of some 10-12 cm., and divides 

 into two bronchi, one proceeding downwards and outwards into each lung. 



Epithelium 



Tunica propria 



Submucous 

 layer 



Cartilage 



Perichondrium 



Fibrous tunic 



FIG. 236. Transverse section of trachea, showing general arrangement of the coats. X 80. 



Until the latter is reached, -the walls of the air-tubes are constant in structure 

 and consist essentially of a fibro-cartilaginous framework,' lined with mucous 

 membrane and covered externally with areolar tissue. 



The cartilage is represented by a series of from sixteen to twenty 

 C-shaped pieces, of the hyaline variety and from 2-5 mm. in width, which 



