1. The results of investigations upon some aspects of anemia in rheumatoid arthritis are reported and discussed.
2. The anemia was essentially normocytic and hypochromic, the mean corpuscular volume being usually normal and the mean corpuscular hemoglobin content and concentration usually reduced. Anemia was more pronounced in the presence of very active disease.
3. Undue hemolysis was not of importance.
4. The myelogram showed no gross abnormality but suggested impaired maturation of normoblasts and retarded hemoglobin formation.
5. The blood and plasma volumes were not essentially abnormal, though the frequent asthenic habitus and loss of weight might produce apparently exalted values in terms of body weight. In the more anemic cases, changes common to many anemias were found, viz., normal plasma volume with decreased corpuscle and whole blood volume.
6. The plasma iron concentration was usually reduced; subnormal values were invariable in cases with very active disease or marked anemia.
7. The iron-binding capacity of the serum might be raised by iron deficiency or slightly reduced but not enough to be a factor in producing or maintaining anemia.
8. As judged by changes in the plasma iron, intestinal absorption of iron after a single maximal therapeutic dose was variable. Some cases showed the excellent absorption and therapeutic response characteristic of simple iron deficiency. Others gave strong presumptive evidence of impaired absorption.