THE DEVELOPMENT OF THE LUNGS. 
BY 
JOSEPH MARSHALL FLINT, M.D., 
Professor of Anatomy in the University of California. 
(From the Hearst Anatomical Laboratory of the University of California.) 
WITH 4 PLATES AND 29 TEXT FIGURES. 
It requires only a cursory inspection of the literature on the lungs to 
show the unsatisfactory state of our knowledge concerning the develop- 
ment of these organs. In the first place, the ontogeny and phylogeny 
of the mammalian lungs have stood in apparent conflict. There are, 
moreover, few features of their anatomy upon which there is any agree- 
ment among the various investigators who have contributed to this field. 
As a reworking ‘of the entire subject has seemed desirable, the author 
was guided in choosmg the pig, first of all, by the practically unlimited 
supply of the different embryonic stages and, secondly, by the fact that 
the artiodactyls possess in well developed form, all of the most discussed 
types of bronchi. 
METHODS. 
For the study of the early stages of the development of the respiratory 
system, the Born reconstruction method was employed. Fruitful sug- 
gestions for its use have been obtained from the contributions of Bar- 
deen and Huber, whose applications of the Born method have been 
followed in this study. Sections of a series of pigs were cut at 20 micra 
and stained in hematoxylin and congo red. The reconstructions were 
made at a magnification of 100 diameters. In order to obtain an ac- 
curate orientation of the subdivisions of the bronchi, the piling of the 
plates according to the external form of the lung was controlled by 
dissections of the lungs of a series of embryos of a corresponding age as 
those, used for reconstruction after the method suggested by Minot. 
Liberal use has been made of the various corrosion methods to follow 
the evolution of the bronchial tree in pigs from 4 cm. to those of adult 
life. The use of Wood’s metal and of celloidin corrosions gave fruitful 
results, although the majority of the stages were obtained by the use 
AMERICAN JOURNAL OF ANATOMY.—VOL. VI. 
