and histological slices of frog (Hyla japonica) and mouse hearts, show the different locations of the branching points of coronary arteries: in the gill artery of the fish, in the carotid artery ...

but agree that the frog's heart, though possessing only a single ventricle, functions, nevertheless, so that the so-called arterial blood, returning by the pulmonary veins, is mixed only slightly ...