1. Guinea pig hemoglobin crystals are shown to be readily permeable to ferricyanide and hydrosulfite, indicating the presence of interstices between the protein molecules of the crystal.
2. The assumptions of closest hexagonal packing and of spherical molecules of HbO2 lead to a crystal lattice having interstices between the molecules which represent 25 per cent by volume of the crystal. These spaces would be just large enough at their narrowest junctures to permit ferricyanide ions to diffuse through them. If these spaces were filled with water, then 20 per cent by weight of the crystals would be water.
3. The hemes are on the surface of the globin and are arranged facing the interstices between the molecules of the lattice.
4. The binding of O2 in HbO2 is stronger in the crystal lattice than in solution.
5. Hydrogen, activated with colloidal palladium, will not reduce ferrihemoglobin except in the presence of a redox dye.
6. In the reduction of O2 by activated hydrogen, H2O2 can be demonstrated by the formation of the H2O2-ferrihemoglobin spectrum.
