330 CHIKANOSUKE OGAWA 
for thirty-five to forty, 0.33 to 0.55 mm. for seventy to eighty. 
In Schulze’s account he gives 0.08 to 0.1 mm. for the new-born, 
0.15 for middle age, and those 0.25 to 0.4 mm. in breadth and 0.1 
to 0.2 mm. in depth for old age. 
I measured in my positive model from the thirty-one-year-old 
man the alveoli in several parts and found the results as given 
in table 2. 
Thus the alveoli in my model on the average measure 0.1 mm. 
in both breadth and depth. 
The results obtained from the measurement of the alveoli of 
my negative model from the fifty-six-year-old man are as shown 
in table 3. 
The alveoli here measure 0.15 mm. in depth and 0.19 mm. 
in breadth. Accordingly, these are larger than those of the 
positive model. But I cannot tell if this difference comes from 
age, the part of the lung studied and the degree of expansion of 
the alveoli. According to Rossignol and Miller, the alveoli in 
the bases of air-saes are larger than the others. I have also 
noticed this fact in my model, but this is not the invariable case. 
SUMMARY 
1. The alveolar ducts divide two or nine times to reach the 
air-sacs. 
2. The angles of ramification of the alveolar ducts are of 
various grades ranging from wide angle to acute. As type of 
ramification both monopody and dichotomy are present in 
an alveolar-duct system. 
3. Diverging planes of alveolar ducts frequently cross each 
other. 
4. The alveolar ducts branch in frequent succession, the de- 
crease in the diameter is not marked. 
5. The mouths of the alveolar ducts consist of alveolar septa, 
but usually the mouths are enclosed partially by the wall of the 
alveolar ducts itself. 
6. Justesen’s rule that the number of side branches corresponds 
to those of the continuation of the trunk and its branch, is not 
true for the alveolar ducts of the adult man. 
