Histopathological changes caused by H. hypnale, H. nepa and H. zara venoms in mouse lungs, brains and spleens. (Note: the histopathological changes caused by the three Hypnale venoms were similar. The dose and the type of venom led to each histopathological change in representative photographs are mentioned within the parenthesis) Note severe pulmonary oedema (a: 2.3 μg/g dose of H. hypnale venom), pulmonary interstitial haemorrhage (b: 3.0 μg/g dose of H. hypnale venom), inflammatory cell infiltrate in alveolar septae (c: 1.4 μg/g dose of H. hypnale venom) in lungs of test mice. Normal alveoli of a control mouse are shown in figure (d: 0.9% sterile NaCl solution). Ishchemic neuronal degeneration in cerebral cortex is shown in figure (e: 5.3 μg/g dose of H. zara venom). Hyperplasia of the red pulp of spleen (f: 1.5 μg/g dose of H. hypnale venom) as evident by large aggregations of immature stages of erythrocytes and presence of megakaryocytes (g: 6.0 μg/g dose of H. nepa venom) seen in splenic red pulp of test mice. Red pulp of a control mouse is shown in (h: 0.9% sterile NaCl solution).