Cellular composition of the late milk of the koala (Phascolarctos cinereus)

The changes in cellular composition of the milk of the koala (Phascolarctos cinereus) have been investigated in late lactation and after the loss of p ouch and back young. During lactation, the polymorphonuclear neutrophil was the most frequently observed cell. After loss or removal of the young, mac rophages and foamy epithelial cells were detected in moderate to high numbe rs. In one animal, mammary secretions containing lymphocytes and unidentifi able, immature mononuclear cells continued for 120 days after the loss of p ouch young. These observations of cellular composition of late- and post-la ctation secretions are consistent with reports from a number of eutherian m ammals and also with another marsupial, the tammar wallaby (Macropus eugeni i).