Histopathological changes caused by a myotoxin from Bothrops jararacussu snake venom. Comparison with the effects of whole venom: L. S. Queiroz, H. Santo Neto, M. I. H. Brandeburgo, L. R. Simioni and J. R. Giglio (Departments of Pathology, Anatomy and Pharmacology, Campinas State University, Campinas, and Department of Biochemistry, Faculty of Medicine, Ribeirao Preto, Brazil)