Histologically, the papillary muscles of the heart of buffalo consisted of three layers; endothelium, subendothelial and myocardial layers from within outwards. Endothelium was a simple squamous epithelium, which was supported by a subendothelial layer which consisted of loose connective tissue mainly collagen, elastic fibers and adipose tissue. The endothelial and subendothelial layers together form an endocardium. The central layer, considered the normal myocardial layer, consisted of cardiac muscle. The muscle fibers appeared long, striated, branched and anastomosed; some binucleated cells were occasionally observed, with centrally placed nuclei having prominent nucleoli. The sarcoplasm of cardiac muscle was eosinophilic, full of parallel contractile myofibrils that consisted of myofilaments with a very strong cross striated banding pattern. The purkinje fibers were organized into bundles at the subendocardial region and in between and surrounding the cardiac muscle bundles. Chordae tendinae also consisted of three layers; outer endothelial, middle subendothelial and central fibrous layer.