Joseph Marshall Flint 113 
the support, which Narath brings from the comparative anatomy, the 
facts are capable of a simpler explanation, 7. ¢., a wide variation in the 
position of the buds and the power of one bronchus substituting for 
another. These two factors which I have followed in detail in the pig’s 
lung, will explain all of the conditions in the adult tree which led first 
Aeby and then Narath and their followers to look upon the ventral and 
medial groups as derivatives of the lateral series. It may also be well 
to call attention to Hesser’s pointed criticism of Narath’s view when he 
remarks that the lateral buds of Narath when they have only reached the 
development of a low round cone with a broad base, represent the anlagen 
of four different branches, namely the dorsal, lateral, ventral, and medial 
bronchi which must isolate themselves and take their places on the 
stem. And lastly, we cannot help noting the lack of the one convincing 
argument which should come from comparative anatomy consisting in a 
primitive lung that possessed only lateral bronchi. 
Furthermore, the series of schematic figures, which Narath gives to 
show the origin of the medial from the dorsal bronchi are objectively 
correct and agree with the conditions found in the pig’s lung not only 
in the embryonic stages but in the adult tree as well. He finds the first 
median division of the dorsal bronchi as one descends from D. 2 to D. 5, 
is placed successively nearer the stem bronchus until, at the latter point 
buds are seen on the dorsal and medial sides of the stem. He interprets 
this condition as indicating a wandering of this median branch to the 
stem. Asa matter of fact, however, this is the normal relationship for 
the grown lung, and, as I have pointed out above, the medial series do 
not occur higher than Lateral 4. It is scarcely justifiable, therefore, 
to interpret the successive change in the insertion of this median branch, 
together with the appearance of the medial buds in their usual position 
as evidence of wandering on the part of the median bronchi. 
In reference to the further division of the tree after the principal 
branches are laid down, Moser, Willach, Narath, Cadiat, Kiittner, and 
Kdlliker believe in a monopodial propagation, while His, Minot, d’Hardi- 
viller, Hesser, and Flint believe in the dichotomous form either equal, 
unequal, or both. 
AEBY’S EP- AND HYPARTERIAL THEORY. 
The substance of Aeby’s views with reference to the influence of the 
pulmonary artery upon the bronchial tree has been given in the abstract 
of his monograph. This theory, which has influenced, more or less, the 
work of all subsequent investigators has been accorded a varied reception. 
8 
