220 ELEMENTS OF HISTOLOGY, [chap.xxvm. 



The lymphatic networks of the bronchial mucous 

 membrane are very conspicuous. Those of the sub- 

 mucous tissue, i.e., the peribronchial lymphatics, anas- 

 tomose with those surrounding the pulmonary blood- 

 vessels. 



Pigment and small particles can be easily absorbed 

 through the cement substance of the epithelium 

 into the radicles of the superficial lymphatics, whence 

 they pass readily into the (larger) peribronchial lym- 

 phatics. 



In connection with the nerve branches in the 

 bronchial wall are minute ganglia. 



289. Each terminal bronchiole branches into 

 several wider tubes called the alveolar ducts, or infundi- 

 bula ; each of these branches again into several similar 

 ducts. All ducts, or infundibula, are closely beset in 

 their whole extent with spherical, or, being pressed 

 against one another, with polygonal, vesicles the air- 

 cells or alveoli opening by a wide aperture into the 

 alveolar duct or infundibulum,but not communicating 

 with each other. The infundibula are much wider 

 than the terminal bronchioles, and also wider than 

 the alveoli. 



290. All infundibula with their air-cells, belonging 

 to one terminal bronchiole, represent a conical struc- 

 ture, the apex of which is formed by the terminal 

 bronchus. Such a conical mass is a lobule of the lung, 

 and the whole tissue of the lung is made up of such 

 lobules closely aggregated, and arranged as lobes. 

 The lobules are separated from one another by delicate 

 fibrous connective tissue ; this forms a continuity 

 with the connective tissue accompanying the bron- 

 chial tubes and large vascular trunks, and with these 

 is traceable to the hilum. On the other hand, the 

 interlobular connective tissue of the superficial parts 

 of the lung is continuous with the fibrous tissue 

 of the surface called the pleura pulmonalis. This 



