464 WILLIAM SNOW MILLER 
hernia-like protuberances of the wall of the main bronchus which 
become gradually more marked and in the end develop into lateral 
bronchi. 
Liihe, commenting on the results obtained by d’Hardiviller, 
says: ‘‘his work may be taken as a confirmation of the statement 
that new side branches always originate exclusively near the dis- 
tal end of the growing bronchus, but no longer from the completed 
bronchial tube.’’ d’Hardiviller takes this as a proof of the mono- 
podial development of the bronchi. In a later study of the lung 
of the sheep d’ Hardiviller states that the branching of the primary 
bronchi is exclusively monopodial, but their division into second- 
ary bronchi is partly monopodial and partly dichotomous. 
Nicholas and Dimitrowa also used the lung of the sheep in 
their study; they reached essentially the same conclusions as 
d’Hardiviller, but go further and claim that even the two main 
bronchi do not originate through a forking of the trachea but 
arise as buds from the dorsal portion of the lateral faces of the 
tracheal anlage. 
Flint has made an extended study of the development of the 
bronchial tree in the pig. His results may be summed up as 
follows: 
The growth of the main series of bronchi is monopodial in character, 
that is to say, they are produced without a definite division of the end 
bud. New elements are not always produced from the end bud, but 
may be formed from the stem some distance from its terminus. The 
process is successive; that is to say, the elements are produced one after 
another from above downwards. . . . . Subsequent division of 
the branches may occur either by monopody or dichotomy. Often 
monopodial production of buds persists for one or two generations on 
the main bronchi, then the method becomes dichotomous, either equal 
or unequal in nature, depending somewhat on the space in which the 
bronchi have to divide. 
My own studies of the bronchial tree of the cat lead me to the 
conclusion that, so far as the main series of bronchi are concerned, 
the mode of branching is monopodial. The mode of division in 
the terminal branches will be considered under a separate heading. 
