Joseph Marshall Flint 
ise) 
OL 
more lateralwards. Its stem is cylindrical in form and it terminates 
im a rounded bud-lke swelling in which mitoses are numerous. No 
evidences of Ventral 2 or Dorsal 2 are seen. If we turn for a moment to 
the consideration of the origin of L. 1, we find the bronchus is a trifle 
more precocious, but practically simultaneous with the second lateral 
branch in its origin. It is separated from Lateral 2 by a considerable 
distance. If the views of Willach and Narath were correct, this branch 
should not appear until later, and should be traceable, step by step, from 
the bud forming right Lateral 2 to its final position on the trachea. Its 
direction is practically lateralwards with a scarcely visible tendency to 
point ventralwards. It would not then, from the topography of its ori- 
gin, bear any analogy to a dorsal bronchus. From this distinctly lateral 
position of its origin, I have classed it among the lateral group of bronchi, 
although, in its subsequent growth, one of its branches extends down into 
TXT IGse alent 2 sand ls: 
Text Fias. 11, 12, and 13. Sections through the right stem bronchus of 
an embryo 10 mm. long. Fig. 11 above, Fig. 12 through, Fig. 13 below the 
origin of Ventral 2 and Dorsal 2. V=—=Ventral. D=Dorsal. C= Pleural 
cavity. S—=Stem bronchus. V.2—Ventral 2, the Bronchus cardiacus. D. 2 
= Dorsal 2. 
the dorsal region giving the bronchus a certain superficial resemblance to 
that series. On the other hand, the lower lateral elements grow ventral- 
wards in the later embryonic stages and thus also lose their early strictly 
lateral character. This much is certain; if L. 1 arises phylogenetically 
from the dorsal group, a view for which there is no convincing proof, 
absolutely all trace of the migration is lost in the pig. It originates like 
one of the lateral bronchi and subsequently develops its superficial re- 
semblance to the dorsal elements. Whatever support for the relation- 
ship of the broncnus to the dorsal series, can be drawn from this fact, is 
multiplied by the behavior of a lateral branch of left L. 2, which does 
exactly the same thing in an adaptative process on the part of the bron- 
chus to a relatively unobstructed environment. 
Similarly, Ventral 2 is produced after the formation of Lateral 2 
simply as an evagination of the walls of the stem bronchus. It occurs at 
