86 The Development of the Lungs 
bronchi. From this time, it is more convenient to consider these stages 
by themselves. In the description of the differentiation of the frame- 
work, I have taken as a basis the work of Mall, 02, who has described in 
the pig the origin of the connective tissues from a common mesodermic 
syncytium. By a differentiation of this syncytium into an endoplasmic 
and exoplasmic portion, the connective tissues are produced. The former 
ESP TE. Zils 
Text Fic. 21. Longitudinal section of the left lung of an embryo pig 
13 mm. long. Fixed in Zenker’s fluid and stained by Mallory’s Fuchsin- 
Anilin blue method. X70. b=Stem bronchus. p=—pleura. a= Young 
connective tissue. =syncytium. m—evagination forming medial bronchus. 
remains as the protoplasm about the connective tissue cells, the latter 
forms the various fibrils. The author, 03, has traced the development of 
the framework of the submaxillary gland in the pig, where, in the earlier 
stages, the process of differentiation is the same as in the lungs. By 
