168 GEO. S. HUNTINGTON 
distinct points on the respiratory area of the stembronchus, or 
of its ventro-lateral derivative, or of both, and the selection of 
one of the three available points for the development of each of 
the three types (fig. 111A, B, C). These three points are fixed 
and do not change their position during the individual ontogeny. 
irs 
Figure 10 
D 
1 2 
Figure 11 
Figs. 10 and 11 Variation in origin of a ventro-medial bronchus. 
When epithelial budding has started at any one of them it will 
continue,and accordingly lead to the corresponding adult con- 
dition of either A, B, or C. 
It happens occasionally that a peripheral lung segment re- 
ceives its bronchial supply from two sources. The terminal 
alveoli of each contributing bronchus are closed off within the 
segment of the district which it supplies and do not communi- 
cate with those of its colleague. Together the two components 
