Fig. 25 
ay Hic. 26 
x 350. 
Fig. 27 
Fig. 28 
. Ve ry 4 ° 
oe ry ACO r i 
2 \ - fe y - , 
oF Ba g z a Cb es eo > 
es Je GP obo: 
RESPIRATORY SPACES OF THE LUNGS ott 
iy AAPL, 
Muscle fibers of the mouth of the alveolar duct. Mole. Hematoxylin-eosin. X 350. 
Muscle fibers of the mouths of the alveolar ducts and alveoli. Dog. Hematoxylin-eosin. 
Elastic fibers. The lung of the bat. Resorein-fuchsin. X 350. 
Elastic fibers. The lung of the rat. Resorein-fuchsin. X 350. Elliptic area in the 
center is the mouth of the alveolar duct. 
