Fig. 4.

(A) Reconstruction of the air-conducting system showing a parabronchial lumen (PL) giving rise to an atrium (At), which forms an infundibulum (If) that in turn gives rise to the air capillaries (AC). Scale bar, 25 μm. (B–D) Respective side views of the combined, airway and vascular reconstructions of the components of the exchange tissue of the lung of the muscovy duck, Cairina moschata. PL, parabronchial lumen; If, infundibulum; AC, air capillaries; BC, blood capillaries. Scale bars, 20 μm.