Informational film about organisms invading the blood. The leukocytes engulf the cubicle bacillus. The bacteria are engulfed by the protoplasm and digested. Shot of swirling cells coming together. Monocytes are leukocytes with one nucleus. Shot of a group of monocytes moving. The membrane is moving about. Cubicle Bacillus looks like white pine needles. Monocytes move and engulf the organisms near it.