470 WILLIAM SNOW MILLER 
DESCRIPTION OF RECONSTRUCTION 
The portion of the lung entering into the reconstruction con- 
sists of a bronchiolus and the air spaces connected with it. The 
walls of the bronchiolus are practically smooth, showing only the 
rugae which are normally present. The bronchiolus divides into 
two branches whose walls bear scattered alveoli. These branches 
will be designated as bronchioli respiratorii a (plate 1). One of 
these branches is carried out. It measures 0.21 mm. in diameter 
and extends in nearly a straight line for about 0.6 mm. It then 
divides into two branches whose walls bear a greater number’ of 
alveoli; these branches will be designated as bronchioli respira- 
torii b (plate 1). Only one of these branches is carried out in 
the reconstruction. This branch measures 0.14 mm.., in diameter 
and extends about 0.35mm. It then divides into three branches, 
the ductuli alveolares. Each ductulus alveolaris is thickly cov- 
ered with alveoli, some of which are of considerable size and re- 
semble sacculi alveolares. 
The ductuli alveolares vary in diameter from 0.11 to 0.12 mm. 
and are about 0.42 mm. in length, measuring to their most distal 
point; but, if we allow for the dilated extremity, they are about 
0.22 mm. in length. Each ductulus alveolaris breaks up into a 
series of air spaces which collectively form a lobule. The three 
lobules thus formed enter into the reconstruction and for con- 
venience of description will be designated by the numerals I, II 
and III (plate 1). 
In the following description the terms of direction are relative, 
and describe the position of the parts in the reconstruction. 
Lobule I.° Ductulus alveolaris I (plate 1, I), extends to the 
left from the median line of the bronchiolus respiratorius from 
which it arises. It maintains practically a uniform diameter and 
shows only a slight dilatation at its distal end. From it arise three 
atria which will be designated la, 1b, le (plates 1, 2). 
Atrium la lies at the distal end of the ductulus alveolaris and 
extends in the same direction as the latter. It measures 0.3 x 
0.2 x 0.28 mm and communicates with the ductulus alveolaris 
