324 CHIKANOSUKE OGAWA 
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wall is concaved on one side and protrudes correspondingly on 
the other side, or it may be totally flat on both sides. This 
flat portion is naturally not beset with alveoli. 
Fig. 6 Diagram of ramification of the alveolar ducts. 
Fig. 7 Diagram of common wall of the alveolar ducts. 
Fig. 8 Diagram of section of alveoli. 
