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From a section of the lung of a cat, stained with silver nitrate. Labels: A. D., alveolar duct or intercellular passage; S, alveolar septa; N, alveoli or air cells, lined with large flat, nucleated cells, with some smaller polyhedral nucleated cells; M, Unstriped muscular fibers. Circular muscular fibers are seem surrounding the interior of the alveolar duct, and at one part is seen a group of small polyhedral cells continued from the bronchus.

Air Cells from a Cat's Lung

From a section of the lung of a cat, stained with silver nitrate. Labels: A. D., alveolar duct or intercellular…