Joseph Marshall Flint 109 
according to d’Hardiviller, give rise to secondary branches by the produc- 
tion of lateral buds as well as by equal and unequal dichotomy. d’Hardi- 
viller does not believe that all branches of the stem are successive in their 
formation. 
Nicholas and Dimitrova, 97, in the sheep, describe the growth of the 
main bronchi as lateral buds which appear successively on the terminal 
portion of the stem bronchus. 
The results of Justesen, oo, contained in an extensive paper devoted 
entirely to the method of growth of the bronchial tree, may be given in 
one sentence, “ Die Bronchialverzweigung ist also eine dichotomische,” 
in which process he would include all branches of the tree from first to 
last. 
The process of growth of the bronchial tree according to Narath, g2, 
96, o1, is a rather complicated process. He looks upon the primitive 
lung sae as the first production of a stem bud. When a side branch is 
produced from the end bud a slight swelling is observed on its lateral 
side, emphasized by the occurrence of mitosis in this region. In conse- 
quence of the greater pressure at this point, the end bud bends slightly 
in the opposite direction, that is to say, medialwards. As the new bud 
grows, this process continues until there is a distinct kink in the axis 
of the stem opposite the new element. As it increases in size, the side 
bud takes first, the form of a cone-like projection with a rounded summit, 
as the stem bud grows on, then the epithelial wall about its base sinks 
somewhat towards the axis of the stem, until the daughter bud is isolated 
from the stem and then grows on. It is important to note, furthermore, 
that Narath considers the end bud the entire terminal part of the stem 
up to the last well-formed lateral branch. 
In reference to the origin of the dorsal bronchi, Narath states from 
his observations on the rabbit, that they are produced without partici- 
pation of the stem bud and that they appear later than the corresponding 
lateral bronchi. Furthermore, the comparative anatomy of the tree 
suggests to him that the dorsal series are primarily side branches of the 
lateral bronchi which, in course of ontogeny or phylogeny are placed 
back on the stem. In support of this view, he finds the dorsal buds 
arising at the same level as the lateral and, apparently, in communica- 
tion with the contour of the latter. Then, he continues, if lateral bronchi 
are able to give up dorsal branches to the stem, this process repeats itself 
with the latter series in giving rise to the median bronchi. While he is 
not absolutely certain that this process takes place in the origin of the 
dorsal elements, he states that it can be proved with certainty in the 
formation of the medial series. He shows a schematic series of draw- 
