Polymorphonuclear neutrophil leucocytes of peritoneal fluid

Cells in the peritoneal fluid from 179 horses were examined in Giemsa stained preparations using light microscopy. Neutrophils were found in all samples whether transudative or exudative although their proportions varied enormously. They were well preserved in "normal" or sterile effusions and hardly differed morphologically from those seen on a peripheral blood film although hypersegmentation was commonly observed. In purulent effusions a reliable correlation was found between degenerative changes in neutrophils such as karyolysis and karyorrhexsis and the presence of toxin-producing microorganisms. On most occasions these degenerative changes enabled a confident judgement to be made as to whether the likelihood of a bacterial aetiology did or did not exist even in the absence of demonstrable microorganisms.