2 9 5 



PRACTICAL HISTOLOGY. 



[XXVII. 



(c.) The submucous coat, composed of more open connective 

 tissue, and continuous with the former. In it are the acini of 



mucous glands ; but as 

 the glands are more 

 abundant in the spaces 

 between the cartilages, 

 their distribution is 

 better seen in a longi- 

 tudinal section. It is 

 rare to find a duct, as 

 they pierce the mucous 

 coat obliquely, and 

 open on its inner sur- 

 face. 



(d.) The mucous 

 coat, composed of 

 fibrous tissue covered 



FIG. 284. L.S. Mucous Membrane of Trachea of Cat. 



by stratified ciliated epithelium. Under the epithelium is a longi- 

 tudinal layer of elastic fibres, which are therefore cut across trans- 

 versely. Within this, a basis of connective tissue infiltrated with 

 adenoid tissue, and internal to this again a structureless basement 



Bronchia! Muse/e. 



Bronchia/ flrfery. 



Garfitcge 



Gfaiicf acini &. c/ucf: 



FlG. 285. T.S. Intra-Pulmonary Bronchus of Cat. PA and PV. Pulmonary artery and 

 vein ; bv. Bronchial vein; V. Air-vesicles. 



membrane, best seen in very thin sections, and best of all in a 

 human trachea. Besting on the basement membrane is the ciliated 

 epithelium. It occurs in several layers, but only the superficial 

 layer of cells is ciliated. In the lower layers of cells three or four 



