HUMAN LUNG 329 
alveolar septum, while the other side may have only the alveolar 
septum. c) The alveolus may be entirely closed by both the 
alveolar septum and the concave wall of the alveolar duct. 
(Such an expression as “the concave wall of the alveolar duct’’ 
may not be adequate, but one can easily understand what I 
mean.) Type A and type B are in fact rarely seen, the greater 
numbers are of the C type. Schulze considers that the mouth 
is smaller than the lumen, but I notice that the mouth is some- 
times larger and at other times smaller. 
TABLE 2 TABLE 3 
DEPTH a, ees Os BREADTH Be etene Oe DEPTH BREADTH 
mm, mm, mm, mm, 
0.04 6 0.05 2 0.20 0.24 
0.05 2 0.06 2, 0.13 0.25 
0.06 7 0.07 9 0.18 
0.07 4 0.09 3 0.19 
0.08 2 0.10 16 0.10 Omit 
0.09 4 Opt 6 0.21 
0.10 12 OR 15 0.10 0.15 
0) atu 3 0.13 2s 0.30 
0.12 8 0.15 4 0.19 0.19 
0.13 2 On7 1 On 0.17 
0.14 By 0.19 1 0.12 
0.15 4 =|. a 0.16 ORs 
O16 1 Ave. 0.10] Total 61 (oe 
0.19 3 Ave. 0.15 0.19 
0.21 1 
Ave. 0.10 | Total 61 
b. The size of alveoli. According to Kolliker, the alveoli 
collapsed after death are one-sixth, one-tenth, and one-eight- 
eenth the size of the normal. Schulze calls attention to the 
fact that alveoli are of different sizes in the various parts of the 
lung, namely, alveoli located near the surface of the lung, espe- 
cially in the apex and edge are larger than those of the inner 
part. Schulze and Rossignol say that the size of these alveoli 
increases with age. Rossignol gives the measurements of alveoli 
according to ages as follows: 0.2 mm. for the ages between 
eighteen and twenty, 0.22 to 0.25 for twenty-five years, 0.25 
