Somatic cells observed in collected mammary secretions. An eosinophil (E), lymphocyte (L), and macrophage (M) are depicted in A. B Depicts two neutrophils collected from a challenged quarter with the bottom neutrophil containing intracellular Staph. aureus (arrow). A binucleated macrophage is shown in C (arrow). These cells are suspected to originate from lumen resident macrophages that undergo incomplete cell division like the mitotic cell (arrow) shown in D. Scale bars = 10 µm.