Figure 4b. (a) Transverse section of mammary tissue from the acute animal after viability staining shows demarcation (circular outline) between nonviable (pale yellow central region) and viable (blue peripheral region) tissue (bar = 1 cm). (b) Photomicrograph obtained in the acute animal shows a mammary lobule (center) surrounded by a nonviable tissue zone. Epithelial nuclei are densely basophilic and pyknotic. Architecture is preserved, which is consistent with acute coagulation necrosis. (Hematoxylin-eosin stain; original magnification, x200.)