1. Hemosiderin may be produced outside of the animal body and is increased in the liver of rabbits, during autolysis, for a period of from twenty-four to forty-eight hours.
2. Post-mortem hemosiderin formation is most marked in parts of livers exposed to air, and hemosiderin is, apparently, an oxidation product of hemoglobin due to enzyme action.
3. Hemosiderin is derived from hemoglobin directly and not from hematin as an intermediate product.
4. The later stages of autolytic changes show that the acid products of proteid autolysis, especially the phosphorus acids, are capable of producing a cleavage of hemosiderin and uniting with the iron to form a new series of products which react microchemically for both phosphorus and iron. In such cleavage, pigments analogous to the bile pigments are formed.
5. The relationship observed between hemosiderin and hematoidin is such as would indicate that hematoidin is the pigment matter of hemosiderin.
6. Further, it seems probable that the vital cycle of hemoglobin metabolism in the liver is largely intranuclear; the hemoglobin is converted into hemosiderin either within the nucleus or cell protoplasm; the iron of the hemosiderin is bound by an acid radicle of the nucleo-proteid, and the hematoidin is excreted as bile pigment.