TERMINALS OF HUMAN BRONCHIOLE Die 
from the sheet of glass, turned upside down, and the other por- 
tion of the model was then built up in the same way. This 
method of orientation was found to be much more economical of 
time than was the use of bridges and entailed no sacrifice of 
accuracy. 
To follow a respiratory bronchiole from its beginning to its 
terminals, it was necessary to, make drawings from 128 sections 
of the adult lung. As each section was 20 thick, it is evident 
that the piece of lung containing all these branches had a thick- 
ness of 2560 un, 1.e., 2.56 mm. or a little over 1/10 of an inch. 
It will be evident also that the height of the completed model 
would be 256 mm., or a little over 10 inches. In the case of the 
child’s lung, drawings of sixty-three sections were required, and 
as each section was 30 » thick, the thickness of the piece of lung 
reconstructed was 1890y, or 1.89 mm., and the height of the 
completed model approximately 7.5 inches. 
RESULTS 
The first impression received from inspection of the completed 
models is that the branchings of a respiratory bronchiole are far 
more complicated than is revealed in the text-books, and one 
feels also that there is difficulty in ‘labeling’ the various parts 
according to the terms commonly used. In some places a num- 
ber of alveoli are represented in the reconstruction as opening 
into a cavity which seems too small to deserve the name of an 
air-sac, while in another place one finds an alveolus which is 
several times as large as the ordinary alveolus. The models 
indicate that the minute passages in the lung are not formed in 
strict accordance with the usual descriptions. The two models 
when placed side by side suggest at once that the child’s lung is 
a miniature of the adult lung, just as the child’s hand is a minia- 
ture of the adult hand, there being no apparent difference in 
complexity of structure. More air-sacs occur in the volume of 
child’s lung represented than in the greater volume of adult lung 
represented in the first model. 
A photograph of the model from the adult lung is shown in 
figure 1. It starts with a non-respiratory bronchiole which is 
