54. The Development of the Lungs 
The lateroinferior branch which serves as the continuation of the main 
bronchus, runs lateralwards, ventralwards, and slightly posterior. This 
has five main divisions, which have, in general, a ventroinferior and 
dorsosuperior course. V.2, the Bronchus infracardiacus, passes median- 
wards, ventralwards, and slightly posterior. The main divisions noted 
in the earlier stages show an increase in their branching. Dorsal 2 ex- 
tends in a dorsoposterior direction and its main branches radiate medial- 
wards, lateralwards, and superior. The third lateral bronchus passes 
lateralwards, ventralwards, and slightly posterior. Its branches run ven- 
trally, dorsally, and in a ventrosuperior direction. V.3 bronchus in this 
specimens is not present. Dorsal 3 has four main branches, which have 
the same general direction as the second dorsal, namely, median, lateral, 
and superior. ‘The fourth lateral bronchus has, at this stage, six main 
divisions, extending superiorly, laterally, and medially. D. 4 runs lateral- 
wards, ventralwards, and slightly posterior, and has seven main branches 
passing in a ventral, dorsosuperior, and dorsoinferior direction. In this 
tree there is a median branch, M. 5, rising from the main bronchus op- 
posite L. 5, the branches of which run in an ventrosuperior and a dorso- 
inferior direction. ‘This bronchus is fairly constant, and is met with 
frequently in corrosions of older lungs. Its origin has been traced in the 
series of reconstructions of embryonic lungs from a medial evagination 
of the wall of the stem bronchus. D.5 passes dorsalwards and slightly 
inferior. It has three main divisions extending medially, laterally, and 
inferior.. The Ventral 5 runs ventralwards, medialwards, and slightly 
posterior, and has a medial and a lateral branch. Lateral 6 passes 
lateralwards, posteriorly, and to a slight degree ventralwards. It is, 
as yet, not long enough to show the ventral curvature, which is more 
marked in the lateral branches of the higher orders. Its branches, at 
this stage, run chiefly ventralwards and dorsalwards. Dorsal 6 projects 
dorsally and slightly posterior and has a single median division, while 
Ventral 6 as yet, has no branches. 
Lateral 2 on the left side, owing to the further apical growth of its 
main division which passes up to the apex of the lung varies even more 
than in the preceding stage from the corresponding branch on the right 
side. ‘This bronchus supplies the apical region of the left ling, which, 
in general, is taken by L. 1 and L. 2 on the opposite side, although the 
total volume of lung tissue is not nearly as great as that combined in 
the territory tributary to right L. 1 and L. 2. The apical branch grows 
almost directly superior, and has six main branches that run chiefly in 
dorsal, lateral, and medial directions. Its first main dorsal branch ex- 
