“…Thus, for example, the repeated administration of phenylhydrazine to rabbits increases their urinary coproporphyrin excretion to nearly 100 pg per day from control levels of approximately 30 pg per day. Lead produces the most marked and most prolonged coproporphyrinuria of any agent knuwn (4), especially if the rabbit is exposed to sunlight or to light from a mercury lamp (5). Peak values of up to 800 pg per day have been observed following this treatment.…”