Fig. 9. (A,B) Views of the ostrich Struthio camelus lung showing an interparabronchial blood vessel (v). Intraparabronchial vessel, circled; t, exchange tissue; p, parabronchial lumen; arrows indicate atrial muscles. Note that interparabronchial septa are lacking in the lung and the atria (open triangle) are very shallow. Scale bars, 5 µm.