AUTHOR'S ABTRACT OF THIS PAPER ISSUED 
BY £HE BIBLIOGRAPHIC SERVICE, APRIL 19 
A CRITIQUE OF THE THEORIES OF PULMONARY 
EVOLUTION IN THE MAMMALIA! 
GEO. S. HUNTINGTON 
Columbia University 
FIFTEEN FIGURES 
The publication of Aeby’s (2) fundamental work on the 
Mammalian Bronchial Tree in 1880 laid the ground work for the 
phyletic interpretation of pulmonary organization. During the 
four decades which have elapsed since its appearance the problem 
has attracted the attention of many investigators. The reason 
for this interest rests on the fact that the morphological condi- 
tions are complex and difficult to analyze from the standpoint of 
their evolutionary significance. 
The determination of the five types of the mammalian bron- 
chial tree by Aeby very soon drew attention to the following 
cognate topics: 
1. The genesis of the divergent forms and their mutual inter- 
relation. 
2. Their possible derivation from a common ancestral bron- 
chial tree by various modifications of the same during the phylo- 
geny and possibly during the mammalian ontogeny. 
3. The significance of the numerical preponderance of pul- 
monary asymmetry among mammalia, with the right lung the 
dominant and more highly developed organ. 
4. The homologization of the individual components of the 
bronchial tree on the two sides in asymmetrical lungs. 
5. The phylogenetic relation of the mammalian lung to the 
avian and reptilian respiratory organs. 
1 Abstract read at the 26th session of the Association of American Anatomists, 
Pittsburgh, Penn., April 19, 1919. 
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