The heart is located just ventral and posterior to the gills. Grasp the white bulbus arteriosis at the cranial end of the heart, and sever the connection to the ventral aorta. Gently pull the heart back caudally, to expose the sinus venosis. Note the white bulbus arteriosis, the muscular ventricle, and the smaller atrium.

A small heart, particularly while still beating, may be preserved whole. Larger hearts should be cut open, examined for adhesions or raised nodules on the endocardial walls or valves.