ABSTRACT
In the AP rat the cellularity of the bone marrow is examined in sections of sternum and femur as these bones show the most consistent cellularity in rats (Cline and Maronpot, 1985; Wright, 1989). Cytology is evaluated by examination of femoral marrow smears; these are taken from all animals at necropsy, except for any which died, where autolysis prevents adequate evaluation. The smears are not examined unless there are changes in the haematology, or the morphology of the haemopoieitic organs, which require further investigation.
