224 ELEMENTS OF HISTOLOGY. [Chap.xxviu. 



bronchial walls, which are supplied by them with 

 capillary networks. 



The lacunae and canaliculi in the wall of the alveoli, 

 mentioned above, are the rootlets of lymphatic vessels, 

 which accompany the pulmonary vessels, and form a 

 network around them ; these are the deep lymphatics, 

 or the perivascular lymphatics. They are connected 

 also with the networks of lymphatics surrounding the 

 bronchi, -i.e., the peribronchial lymphatics. The root- 

 lets of the superficial air-cells empty themselves into 

 the sub-pleural plexus of lymphatics, a rich plexus of 

 large lymphatics with valves. All these lymphatics 

 lead by large trunks into the bronchial lymph glands. 



295. Between the flattened transparent epithelial 

 cells lining the alveoli are minute openings, stomata 

 (Fig. 128), leading from the cavity of the air-cells into 

 the lymph lacunae of the alveolar wall. These stomata 

 are more distinct during expansion, i.e., inspiration, 

 than in the collapsed state. Inspiration, by its ex- 

 panding the lungs, and consequently also the lym- 

 phatics, favours greatly absorption. Through these 

 stomata, and also through the interstitial cement 

 substance of the lining epithelium, formed particles 

 such as soot particles of a smoky atmosphere, 

 pigment artificially inhaled, cellular elements, such 

 as mucus or pus corpuscles, that have been car- 

 ried into the alveoli from the bronchi by natural 

 inspiration, germ-particles, <fec., find their way into 

 the radicles of the lymphatics ; thence into the peri- 

 vascular and sub-pleural lymphatics, and finally into 

 the bronchial glands. 



