. Quain's elements of anatomy . ed as IroncMa, IroncMolcs, orhroncMal hides, which, diverging in all directions, never anastomose, butterminate separately. The larger branches diverge at acute angles, butthe more remote and smaller ramifications spring less acutely. After acertain stage, of subdivision each bronchial tube, reduced to a small size(about 1 mm.), is termed a lobular or respiratory Ironchial tute(Kolliker), and its walls become beset with small hemisphericalsaccules, termed air-cells, or alveoli. They occur at first only here andthere and confined to one side of the tube only, but
. Quain's elements of anatomy . ed as IroncMa, IroncMolcs, orhroncMal hides, which, diverging in all directions, never anastomose, butterminate separately. The larger branches diverge at acute angles, butthe more remote and smaller ramifications spring less acutely. After acertain stage, of subdivision each bronchial tube, reduced to a small size(about 1 mm.), is termed a lobular or respiratory Ironchial tute(Kolliker), and its walls become beset with small hemisphericalsaccules, termed air-cells, or alveoli. They occur at first only here andthere and confined to one side of the tube only, but at length almostcover it so that the tube in great measure loses its cylindrical length it ends in an enlarged completely sacculated passage termedthe alveolar passage, from which are given off blind ramifications. STEUCTITEE OF THE BEONCHIAL TUBES. 515 somewhat enlarged towards their extremities, and everywhere closelybeset with the air-cells. These enlarged terminations are namedinfundibula (fig. 446). Fig. Fig. 444.—Poktio:n- of a teansverse section of a bronchial tube, human (6 3iii. indiameter) (F. E. Scliiiltze). Magnified 30 diameters. a, cartilage and fibrous layer with inucous glands, and, in the outer part, a little fat;in the middle, the duct of a gland opens on the inner surface of the tube ; h, annularlayer of involuntai-y muscular fibres ; c, elastic layer, the elastic fibres in bundles whichare seen cut across; d, columnar ciliated epithelium. Within the Inngs the air-tubes are not flattened behind like the bronchiand trachea, but form completely cylindrical tubes. Hence, although Fig. 445.
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