The Post Hypoxic Bone Marrow and Spleen Composition

The qualitative and quantitative cellular changes in the bone marrow and spleen of mice during post‐hypoxic re‐adaptation to normal atmospheric pressure were studied. Ten days of hypoxia at about 6,000 m enhanced the number of erythroid cells in the bone marrow and spleen three and twelve fold respectively. The number of lymphoid and myeloid cells falls to about 25% and 50% of the normal values in the bone marrow, in the spleen only the lymphoid cells were moderately depressed. The post‐hypoxic suppression of the erythropoiesis was almost complete in both organs. The myeloid and lymphoid components of the bone marrow began to proliferate about 24 hours after hypoxia. The number of myeloid elements reached the control values between the third and fourth days, the lymphoids recovered slowly with an overshoot between the sixth and eight days. The first signs of the renewed erythropoietic activity were seen after the tenth post‐hypoxic day.