PULMONARY EVOLUTION IN MAMMALIA 165 
medial excentric position in reference to the axis of the entire 
organ. j.4 A 
_ 3. They differ in number and in the details of their peripheral 
extension in the lungs of different mammalian groups, but are 
of fairly constant arrangement in individuals belonging to the 
same species. | f= fo =bo% 
4. By virtue of its universal capacity for the development of 
bronchial buds the stembronchus may produce smaller and less 
regular proliferations in addition to the two principal rows of 
the primary dorsal and ventro-lateral bronchi, in the intervals 
between them. 
Fig. 9 Schema of derivatives from mammalian stembronchus. V., ventral 
bronchi; V/., ventro-lateral bronchi; L., lateral bronchi; DI., dorso-lateral bron- 
chi; D., dorsal; Dm., dorso-medial; M., medial; Vm., ventro-medial. 
For descriptive purposes the derivatives from the axial canal 
may therefore be designated as, Dorsal, dorso-medial, medial, 
ventro-medial, ventral, Ventro-lateral, lateral, dorso-lateral. Of 
these the representatives of the dorsal and ventro-lateral groups 
are selected for the development of the primary principal branches 
of the bronchial tree. To respect Aeby’s priority and for the 
sake of brevity we use the term ‘ventral’ to designate the mem- 
bers of the ventro-lateral group (fig. 9). 
The circumference of the stembronchus thus becomes divided 
into two unequal sectors, a shorter lateral and longer medial, 
between the rows of the main dorsal and ventro-lateral deriva- 
tives. The former contains two secondary points for bronchial 
proliferation, the lateral and dorso-lateral, while on the longer 
