Peritoneal fluid from a horse with colic: The fluid had an increased total nucleated cell count, which consisted largely of non-degenerate neutrophils (>90%) with fewer macrophages. Note the nuclear chromatin is condensed and there is neither nuclear nor cytoplasmic swelling, indicating a lack of degenerative change. The horse had a primary peritonitis due to Actinobacillus equuli. The latter organism frequently does not cause degenerative change in neutrophils, indicating the lack of degeneration in neutrophils does not rule out a bacterial infection (Wright’s stain, 50x objective).
