THE LUNG 



305 



SR\ 



// 



FIG. 289. A BRONCHUS FROM THE HUMAN LUNG. 



a, lining epithelium; b, duct of a mucous gland; c, muscularis nmcosa-; </, accu- 

 mulated mucus, etc., bathing the surface of the epithelium; e, mucous glands;/, 

 hyaline cartilage; y, outer fibrous coat; h, pulmonary alveoli. Hematein and eosin. 

 Photo. X 34. 



developed nnixcularis mucosce composed of interlacing bundles of circular 

 smooth muscle fibers. This layer forms a complete muscular coat \vhieh 

 20 



