IT WAS FOUND THAT THESE SUBSTANCES AND BLOOD REACT IN A SIMILAR FASHION TOWARD THE COMMON PRESUMPTIVE TESTS FOR BLOOD, BOTH REMAINING ACTIVE AFTER HEATING AND PROLONGED DRYING. THE EXPERIMENT DEMONSTRATED THAT AEROBIC MICROORGANISMS ARE A POSSIBLE SOURCE OF ERROR IN THE INTERPRETATION OF THE PRESUMPTIVE TESTS FOR BLOOD. THE AUTHORS SUGGEST THAT CAUTION BE EXERCISED IN THE INTERPRETATION OF THESE SCREENING TESTS, PARTICULARLY WHEN TRACE AMOUNTS OF BLOOD ARE SUSPECTED OF BEING PRESENT. IN ADDITION, ITEMS OF EVIDENCE WHICH MAY CONTAIN BLOOD SHOULD BE PROTECTED FROM BACTERIAL PROLIFERATION. IT IS THE OPINION OF THE AUTHOR THAT IMMUNO-CHEMICAL TESTS, SHOULD BE EMPLOYED WHEN THE PRESENCE OF BLOOD MUST BE ESTABLISHED BEYOND DOUBT. (AUTHOR ABSTRACT MODIFIED)