In the animals given phenylhydrazine, the mean erythrocyte survival time was 5 days. The plasma iron turnover rate was increased about fourfold, and the rate of erythropoiesis was four to five times greater than that in the control pigs.

In the pyridoxine-deficient swine, the mean erythrocyte survival time was within the limits of normal. The plasma iron turnover rate was increased fourfold, but the rate of erythropoiesis was approximately one-fourth the normal mean value. These data are interpreted as indicating that the anemia associated with this deficiency is a result of an inability of the bone marrow to produce a normal number of erythrocytes.

In the pteroylglutamic acid-deficient swine, the mean erythrocyte survival time was 17 days. The plasma iron turnover rate was 5 times the normal mean value. The rate of erythropoiesis was 1.6 times greater than the mean value in the control pigs. These data are interpreted as indicating that anemia develops in this deficiency as a result of a combination of a shortening of the erythrocyte survival time and a limitation of the capacity of the bone marrow to increase red cell production to the same degree as a normal marrow.

The radioactivity in the liver, spleen, and bone marrow of the pteroylglutamic acid-deficient swine, as determined by measurement of the radioactivity over the body surface, declined more slowly than in control pigs.