1. Our data indicate that the effectiveness of whole liver in the treatment of nutritional anemia in rats induced by a milk diet is directly proportional to its available iron and copper content. The other constituents in liver are not needed for maximum hemoglobin regeneration on a diet of milk, iron, copper, and manganese.
2. Commercial preparations of liver products with iron or iron and copper vary greatly in their hemoglobin-regenerating efficiency in rats with nutritional anemia. The variation is correlated directly with the iron and copper content of the preparation. When the copper-iron ratio was too wide hemoglobin regeneration was checked, although the iron supply was sufficient for optimum regeneration.