1. The morphology of the erythrocytes has been studied in 22 normal swine, 65 swine deficient in copper, and 16 swine deficient in iron. The mean values (± the standard deviation) for the volumes of packed red cells in the three groups were 42 ± 2.5, 21 ± 6.6, and 21 ± 6.1 ml/100 ml., respectively. The mean values for the mean corpuscular volumes were 55 ± 3.1, 43 ± 7.1, and 36 ± 5.3, respectively. The mean values for the mean corpuscular hemoglobin concentrations were 33 ± 1.1, 29 ± 2.3, and 28 ± 3.0, respectively.
2. The addition of 11 water-soluble B vitamins, 4 fat-soluble vitamins, ascorbic acid, and minerals (with the exception of copper) to the copper-deficient milk diet did not prevent or delay the development of anemia, modify the morphology of the red cells or alter the degree of hypoferremia.
3. The normoblasts in the marrow of a copper-deficient pig were similar morphologically to those in the marrow of a pig deficient in iron.
4. The intravenous administration of one Gm. of iron, given prior to the development of copper-deficiency, did not delay or prevent the development of anemia.
5. It is concluded that the anemia of copper-deficiency in swine is morphologically similar to the anemia due to iron deficiency in swine.