94 The Development of the Lungs 
invaginations between the mucosal folds appears an ingrowth of glands, 
containing partly serous cells and partly mucous cells which penetrate 
sometimes as far as the muscularis and sometimes between its bundles 
into the submucosa between it and the bronchial cartilages. In general, 
the relations of the lymphatic system (Fig. 26/) have not changed, but 
Thxt EKie. 26. 
Text Figc. 26. Lobule of the lung from a pig 19.cm. long. Same preparation 
as used with the tissue shown in Fig. 21. X70. b=bronchus. p—pleura. 
i1=lymphatics. c—end buds. a@—connective tissue. 
the connective-tissue lobules (Fig. 26) containing the growing ends of 
the bronchial tree have increased considerably in size. The framework 
(Fig. 26a) is denser around the end buds (Fig. 26 ¢), which, while still 
lined by flat cubical epithelium, now show a dilatation of their lumina 
preparatory to the formation of the respiratory lobules of Miller. 
In pigs about 22 cm. long (Fig. 27), the chief changes are in the grow- 
