The words "pigment metabolism" should mean the general exchange and balance in the body of all pigment substances—the income of pigment forming material, the story of pigment building in the body, the disposition of recognized end products in the body and the elimination of certain pigment complexes.
Any junior medical student can relate the true story of pigment metabolism in the human body. The medical textbooks have long retold the story as illustrated in Figure 1; and it seemed to be one of the facts in physiology which stood firm in the midst of progress and newer investigations. Its very age gave it respectability and true academic security of tenure. The time honored story is as follows: Certain food elements and iron are constructed in the bone marrow into a complex substance, hemoglobin. When the red cells are worn out or destroyed, the hemoglobin appears as bile pigment in a