(A) Representative field from a cytospin preparation of buffy coat from a normal mouse, stained as described in Materials and Methods. Black arrow indicates a monocyte identified by the dark blue precipitate. White arrow indicates a neutrophil nucleus (final magnification × 1,000). (B) Representative field from a cytospin preparation of buffy coat from a mouse treated with M-CSF, 4 mg/kg/d, for 4 days. Cells were stained as described in Materials and Methods. Black arrows indicate six monocytes identified by the dark blue precipitate. Note the relative increase in the number of monocytes (final magnification × 1,000).