108 The Development of the Lungs 
“Ich glaube vielmehr, dass beim Menchen, wie bei den Siugethieren, die 
Sprossung eine sogen monopodische ist, welche darauf beruht, dass das 
Mutterrohr vor seinem kugeligen Endblischen eine Verengerung seines 
Lumens erfahrt, wahrend das Lumen des Endblischens sich erweitert 
und seitliche Ausbuchtungen treibt, jene Knospen, die wieder zu Réhren 
werden, und das Mutterrohr weiter fortwichst. Das Tochterrohr ist 
enger als das Mutterohr.” 
The growth process is described by Robinson, 89, in these words: “ In 
the rat and the mouse, the ramification of the bronchi is produced princi- 
pally by dichotomy. The germ of each bronchus, as it grows outwards 
and dorsally, becomes expanded at its termination; this expansion is 
gradually constricted into two portions of unequal size, that is the dicho- 
tomy is in the form described by botanists as unequal or sympodial.” 
Further he states: “ Although most of the branches are produced by 
dichotomous division of terminal expansion, certain of the dorsal branches 
arise as hollow buds from the wall of the stem bronchus after it has as- 
sumed its cylindrical form, and these buds are interpolated between pre- 
existent branches.” He describes the origin of our median bronchi in the 
rat as follows: “The second dorsal branch immediately after its origin 
is similarly divided, and the constriction passes rapidly towards the axial 
stem, until its apex reaches the level of the circumference of the main 
bronchus. Thus, from the dorsal bud, a dorso-internal (median) branch 
is formed.” Robinson apparently does not believe that the branches 
are successive in their formation. 
Minot, 92, states that “the branching occurs in a highly characteristic 
manner, for the stem always forks, but the forks develop unequally, one 
(terminal bud) growing more rapidly and becoming practically the con- 
tinuation of the main stem, while the other (lateral bud) appears as a 
lateral branch. Speaking in general it may be said that the ventral fork 
serves as the stem. In consequence of this method of growth the adult 
lung consists of main stems with lateral branches. . . . But it is erro- 
neous to suppose, as did Aeby, that the system of growth is strictly 
monopodial, it being in reality a modified dichotomous system. The 
branches all arise by terminal forking, never as outgrowths from the side 
of a stem.” 
d’Hardiviller, from his studies on the rabbit and sheep, announces the 
following law of development: “Toutes les bronches primaires, princi- 
pales ou accessoires, naissent en divers points des bronches souches par 
ramification collatérale, le bourgeon terminal des bronches souches ne 
prenant aucune part a leur formation.” ‘These principal branches then, 
