PULMONARY EVOLUTION IN MAMMALIA 175 
favorable site for the exercise of this power, owing to local con- 
ditions described in detail below (cf. infra, p. 186). A new 
bronchial bud (fig. 14, Hp) pushes out into the interval developed 
04 (D1) 
05(Dn)~ ye 
v5 (v0) 
v7(vW) 
Ss 
Figure 15 
by rotation of heart and oesophagus between the foregut, sup- 
porting the right vagus nerve, and the right pulmonary artery, 
and develops into a bronchus which eventually supplies the cran- 
ial area of the upper lobe and enables it to expand further. This 
