Figure 7.  This figure is a electron micrograph of alveoli(a), where gas exchange occurs in the lung, and their surrounding capillaries (c).  The *'s are red blood cells leaving the capillaries and entering the alveoli.  The large open arrows at the top are white blood cells waiting to engulf the red blood  cells.  (Figure from West JB et. al.  Stress failure of pulmonry capillaries in racehorses with exercise-induced pulmonary hemorrhage. J. Appl. Physiol. 75 (1993) 1097-1109.)