Joseph Marshall Flint 115 
tree. On account of the association of this influence with the terms 
“ eparterial ” and “ hyparterial ” it is, perhaps, well to abandon them as 
Zumstein and Narath have suggested. However, this much is certain: 
The theory ought not to be abandoned without an acknowledgment of 
our indebtedness to it. That the theory would stand or fall from the 
results of embryological research, Aeby clearly recognized, much more 
clearly apparently than some of his critics. As a working hypothesis, 
his view was generally accepted from the time of its publication until 
the appearance of Narath’s paper. 
1sT LATERAL BRONCHUS. ‘“‘ EPARTERIAL”’ BRONCHUS OF AEBY. 
This, Aeby regards, as a dorsoventral bronchus which lies above the 
pulmonary artery and, therefore, not under its influence. If it were 
in the hyparterial region the artery would divide it into dorsal and 
ventral bronchi, a view in which Aeby is supported by His. It is an 
independent structure; it may be either paired or suppressed. ‘These 
characteristics form the basis of Aeby’s classification of the mammalian 
lungs. Willach first proposed the idea that this was a branch of the Ist 
ventral bronchus, while Robinson, like His, believes it is an unpaired 
and independent branch. Zumstein in abandoning the eparterial theory 
terms this the first lateral bronchus. Narath uses the expression Apical 
bronchus and takes the same view as Willach inasmuch as he considers 
it a branch of the 1st ventral bronchus. The former, however, goes 
further in regarding this element as a definite dorsal bronchus. This is 
compatible with his tentative view of the whole series of dorsal bronchi 
arising probably primarily from the ventral group. Minot supports Wil- 
lach, while d’Hardiviller thinks it is an independent element arising 
from the trachea in sheep and the stem bronchus in rabbits in which 
view he is upheld by Nicholas and Dimitrova so far as his observa- 
tions in the sheep are concerned. Justesen, Merkel, and Blisnians- 
kaja follow Willach. The unique and remarkable observation of 
d@’Hardiviller, who states that in the rabbit there exists primitively an 
eparterial bronchus on each side, is the only suggestive evidence of the 
degeneration of an eparterial bronchus taking place during the ontogeny 
of the embryo. For a time each develops symmetrically and then later 
the left atrophies and disappears. Upon this observation d’Hardiviller 
concludes that Aeby, His, Robinson, Narath, Nicholas, and Dimitrova 
are mistaken in stating no bronchus arises at this level on the left side, 
and, believes in consequence, Aeby’s classification of mammalian lungs 
is only of secondary value. In certain species they may both develop, 
