Abstract
As stated in previous papers of this series,1 it is probable that porphyrin arises within the body during the process of synthesis of hemoglobin, protoporphyrin III composing the prosthetic group of hemoglobin, myoglobin and various respiratory ferments,2 and that porphyrin of isomeric series I, which arises as a useless by-product during this synthesis, as well as any porphyrin of isomeric series III that is not utilized, is excreted in the urine and feces as coproporphyrin. The total amount of coproporphyrin excreted as well as the ratio of urinary to fecal excretion depends chiefly on the rate of production of porphyrin and the efficiency of the liver, which is the more important organ of excretion of porphyrin, the kidneys normally excreting but a small fraction of the total porphyrin excreted.3 It has been demonstrated that in the event of parenchymatous hepatic damage the ratio of urinary excretion to

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