Joseph Marshall Flint att 
LoBE FORMATION IN THE LUNGS. 
The relation of the mesoderm to the primitive tree has been described 
in connection with the appearance of the bronchi, largely because it 
arises from the general mesoblast of the head gut and takes part in the 
separation of the pulmonary anlage from the cesophagus. The meso- 
lu 
i Le 
ST ST 
Thx) HEiGs. db: 
Text Fic. 15. Outline drawing of the lungs of an embryo pig 10 mm. long. 
Ventral view. (Figs. 15-19-24, inclusive, drawn with a camera lucida from 
cleared preparations.) L.1, L.2—=Swellings, limited by shallow grooves, 
over Lateral 1 and Lateral 2. S7’—=Mesoderm over the caudal portion of the 
stem bronchi. Also L.1—=Lobus superior. L.2—=Lobus medius (right) 
and Lobus superior (left). SZ—Lobus inferior. 
derm, it will be remembered, shows the influence of the first irregularity 
of the early branches of the tree and forms two indefinite unequal 
rounded projections into the primitive ccelom on either side. These 
Li li 
(Le L2 é ie 
L3 \ 
V2 L3 
i ST L3 V2 Ls 
| ST ST 
ie B 
ixeT IG slo 
Text Fic. 16. Outline drawing of the lungs of an embryo 12.5 mm. long. 
A. Ventral view. B. Dorsal view. 2.1, L.2, L.3, V.2, and ST =Swellings 
over the several bronchi and the stem designated by these abbreviations. At 
this stage the anlagen of the lobes are complete. L.1—=Lobus superior, L. 2 
= Lobus medius (right), Lobus superior (left). V.2—Lobus infracardiacus. 
L.3 and ST =Lobus inferior. 
are the anlagen of the two lung wings. On both sides the Recessus 
pleuroperitonealis projects upwards and somewhat medialwards to the 
bronchi; the left, however, is very poorly developed. Ventralwards the 
mesoderm continues forwards into the Mesocardium posterior. 
