462 WILLIAM SNOW MILLER 
two branches again divide, each into two branches, one of which shows 
a somewhat larger caliber than the other. Beyond this the branching 
becomes irregular and the monopodic type becomes obscured. Through 
this strictly monopodic method of branching of a bronchus : 
Aeby’s theory seems to me as much as proven. 
Lithe, commenting on the above quotation, says he can find 
nothing in his description which would exclude the assumption 
of an unequal dichotomous division. 
We have just seen that there is a wide difference in the con- 
clusions reached by those who have studied the mode of division 
in adult lungs by means of corrosion preparations. If now we 
turn to developmental studies we find just as wide a difference, 
as a comparison of the work of d’Hardiviller and of Flint on the 
one hand with that of Justesen on the other will show. 
His was the first, after the appearance of Aeby’s brochure, to 
study the development of the bronchial tree. He describes in 
the lung of man a mixed type of division; the first divisions being 
monopodial, while in their growth the new bronchi originate by 
a dichotomous division of the end buds, not from the already 
cylindrical root tubes. 
Robinson reached practically the same conclusion as His from 
studies made on the lungs of rats and mice; but in addition he de- 
scribes single dorsal branches which arise, between bronchi al- 
ready established, as buds from the walls of the main bronchus 
after the latter has attained its cylindrical form. These are the 
accessory branches of Aeby and of Narath. 
It is somewhat difficult to place the type of division as de- 
scribed by Narath. If one follows the text of his various articles, 
he must be placed in the list of those who believe in the monopo- 
dial or, as Flint has classified him, a modified monopodial type 
of division. If, however, a careful study of his illustrations be 
made, it will be seen that they show a marked dichotomy. 
Guieysse examined the musculature of the trachea and bron- 
chi of the rabbit, guinea pig and other animals and compares 
his results with those of Aeby. The musculature of the trachea 
shows a variable position in different animals; it being attached 
‘In some to the outside of the cartilage, in others to the inner sur- 
