Hearts of human, buffalo, pig, goat and dog (25 of each) were procured from various sources and preserved in 10% formalin. Cardiac veins were dissected to observe their commencement, course, termination and tributaries in all these mammals.

In goat, small cardiac vein was absent and small venules drained right atrium and venticle into right atrium separately. In buffalo, pig and dog small cardiac vein ran into coronary sulcus with the circumflex branch of right coronary artery to open into right atrium separately. Only in human small cardiac vein drained into right extremity of coronary sinus. Marginal vein travelling the left border of heart from apex to coronary sinus was present only in goat.

Only in dog middle and great cardiac veins were formed by union of venae comitantes of posterior interventricular and anterior interventricular arteries respectively near the coronary sulcus. In rest of the mammals middle cardiac vein travelled in posterior interventricular sulcus and great cardiac vein in anterior interventricular sulcus. In all the mammals studied great cardiac vein opened into left extremity of coronary sinus. In human and buffalo, middle cardiac vein opened into coronary sinus near its right extremity while in pig, goat and dog it opened into right atrium near the right extremity of coronary sinus.

In all the mammals studied coronary sinus was present between left atrium and ventricle on the back of heart and commenced as continuation of great cardiac vein to open into right atrium near the crux of heart.