PLATE 2. Histology (A,C,D) and immunohistochemistry (B,D,F) of tissues from the uterus and retained placenta from an aborting bison cow found in March 1995 adjacent to the YNP. A. Necrosis and exudate, placenta. B. Strong labeling of bacteria in trophoblastic epithelial cells. C. Non-necrotic areas of the placenta. D. Lesser amounts of bacteria in non-necrotic areas of the placenta. E. Lung: hyperemia with necrotic debris in a large bronchiole (center). F. Bacterial debris in bronchiolar lumen are stained. Source: Courtesy J. Ryhan.