Joseph Marshall Flint 55 
tends dorsalwards and slightly posterior, and bears a strong resemblance 
to the series of dorsal bronchi from the stem bronchus. Its branches 
run medially, laterally, and dorsoinferiorly. The continuation of the 
main bronchus, the lateroinferior branch, corresponds in its course prac- 
tically to the main branch of the opposite side. It possesses seven main 
divisions, which run dorsosuperiorly, ventroinferiorly, and dorsoin- 
feriorly. 
There is, as usual, no Ventral 2 on the left side. Lateral 3 runs later- 
ally, ventrally, and shghtly posterior. At this stage it has seven main 
branches, which pass dorsally, ventrally, superior, and inferior. While 
the remainder of the branches on the left side below this point show 
many asymmetrical arrangements from the corresponding divisions on 
the right, the architectural characters are sufficiently similar to avoid a 
repetition of the description. The main idea of these tabulations is to 
show the successive appearance of the chief bronchi of the adult lung 
and to indicate how the divisions are adapted to the space relationships 
to which the growing tree must adapt itself. It is not to be supposed 
that simple mechanical conditions govern entirely the growth of the 
bronchi, as its chief architectural features are undoubtedly phylogenetic. 
This much, however, is certain, that there remains always a considerable 
adaptability on the part of the growing branches, which is shown in their 
substitution power when one of the usual elements is suppressed, and 
apparently by the ability of either fork from a division to serve as the 
stem. 
Following is a tabulation of the branches of the tree at this stage: 
TRACHEA. 
Ie ale 
(Ay toe 
(3) D-L-M-L-D-L-M. 
(2) VS. 
(3) DS-LI-LI-DS-LI. 
Tae de Ta. 2: 
CALE (2) Apical. 
(3) D-I-D-V-DI-D. (3) D-L-D-M-V-D. 
C2) ear. (2) BT. 
(3) VI-DS-I-DS-VI. (3) DS-VI-DI-DS-VI-D-I-D-S. 
Wied: ; 
C2) er 
(3) 2DIr 
(2) VS. 
(ie 
(2) VE. 
(3) LI-VI. 
