316 



THE ORGANS 



to six narrow passages — alveolar passages or alveolar ducts (Fig. 215, 

 ^^) — from which are given off the alveoli — air vesicles or air cells* (Figs. 

 214 and 215, d). The somewhat dilated distal end of the alveolar 

 passage is sometimes designated the alveolar sac or infundibulum 

 (Fig. 215, /). Laguesse divides the lobule schematically into three 

 parts a proximal part containing the intralobular bronchus and 



Alveolar sacs 



Blood-vessel 



Terminal bronchus 



Alveoli ssT 



Small bronchus.. 



Fig. 214. — Section of Cat's Lung (Szymonowicz), surface lobule; terminal bronchus 

 opening into alveolar duct from which are given off two alveolar sacs. 



collaterals, a middle part in which the main division of the lobular 

 bronchus occurs, and a third part containing the alveolar bronchi 

 and alveoli. 



The terminal bronchus (Figs. 213, 214, 215, ha). The proximal 

 portion of the terminal bronchus is hned by a simple columnar 



* The dilatation of the terminal bronchus from which are given olY the alveolar 

 passages is sometimes called the vestibule (Fig. 215, v). 



