The morphology of cells in effusions settled on glass.

The cells of human body cavity fluids were examined by light microscopy and with a scanning electron microscope after settling on the surface of glass. Some differences in behavior of various cell types were noticed. The histiocytes, a few minutes after settling, began to spread, and thin processes later extended from their cytoplasm. Extension of mesothelial cells was observed a few hours after settling, and was not proceeded by flattening. The flattening of neutrophils occurred soon after settling, and was not followed by extension. The other cells encountered in effusion, both benign and malignant, did not change their shape even up to 12 hours after the time of settling. The differences in behavior after the settling of various cell types encountered in human effusions is discussed in relation to their biological properties.