(1) Seventeen cases of acute leukemia with Auer bodies have been reported. Studies were carried out on 7 cases of acute monocytic leukemia and 3 cases of subacute myelogenous leukemia.
(2) Histochemical studies showed the Auer bodies to be oxidase, peroxidase, and periodic acid-Schiff positive; sudanophilic, slightly metachromatic and to give positive tests for acetal lipids and ribonucleic acid.
(3) The Auer bodies were negative for acid and alkaline phosphatase, lipase, glycogen, desoxyribonucleic acid and were non-birefringent.
(4) A change in the chemical nature of the Auer body from an acid condition to a more neutral state was noted. This change corresponded with the changes of the normal cytoplasmic granulation of the myelocytes and monocytes during maturation.
(5) The effects of cellular movements, trauma, and temperature changes upon the Auer bodies were studied.
(6) Several leukemic cells, containing Auer bodies, were studied during the process of mitosis.
(7) A theory as to the formation and disintegration of the Auer bodies has been presented.
ACKNOWLEDGMENTS The author wishes to express his thanks to Dr. B. K. Wiseman, Dr. B. C. Houghton, Dr. R. A. Knouff, and Dr. E. R. Hayes for their help and suggestions, and to Dr. J. D. Thomas, Dr.J. F. Gamble, Dr. R. J. Rohn, Dr. H. Schiro, Mrs. Jo Myers, M.Sc., Miss Georgia Gwinner, M.T., Mrs. Susan Ragsdale, M.T. and Mrs. Jeanne Marie Willison, M.T., for their help in securing the experimental material.