Slide 135 - colon. Look at the large blood vessels in the fibrous connective tissue deep to the glands; most of the vessels are filled with erythrocytes, some lying flat, some lying on edge. Notice how pliable RBC's are in shape. Scattered among the RBC's are leukocytes of various types; can you identify any of them? What is meant by rouleaux formation of RBC's in the event of stagnant circulation?