o/2) 
(0/6) 
The Development of the Lungs 
In a pig 30 mm. long (Fig. 22), the framework of the entire lung 
shows a differentiation into primitive fibrils. The young fibrils are 
more distinct and less granular, while the spaces between are larger 
than in the preceding stage. With the differentiation, the relative quan- 
tity of endoplasm has diminished in the loose part of the syncytium, 
leaving in some places isolated connective-tissue cells (Fig. 22.¢), or in 
TexT WIG. Zo. 
Text Fig. 23. Section of the lung of an embryo pig 5 cm. long. Same 
preparation as used with tissue shown in Fig. 21. x 70. p=pleura. a= 
connective tissue. = bronchus. 
others they are multipolar in appearance with branching and sometimes 
anastomosing processes. Immediately about the trachea and large 
bronchi, the cells are closely packed together preparatory to the pro- 
duction of the various coats of these structures. The basement mem- 
brane is distinctly fibrillated as is seen at points where the plane of sec- 
tion is tangential to the bronchi. About the larger bronchial elements a 
