Cellular composition of the bone marrow in the chicken. I. Identification of cells.

Incorporation of Fe55 in vivo was used for verifying on radioautographs the identity of chicken bone marrow cells that are in the process of hemesyntheses. Under the experimental conditions all labeled cells may be considered to be linked with erythroid differentiation. They were classified into five maturational stages according to their morphology and capacity for DNA synthesis. Granulocytes were identified by the presence of specific granules. All mononuclear cells were classified as lymphocytes which had a pachychromatic nucleus, a high nucleocytoplasmic ratio, lacked the capacity for DNA synthesis, and resembled small lymphocytes of the bursa, spleen and bone marrow that bound, in vitro, anti-chicken gamma globulins labeled with I125. Radioautography with H3TdR was used to identify proliferating and non-proliferating members of each cell population.