The heart of a mammal is.....

The Eustachian valve, which is of no significance in the adult mammal, is a vestigial organ. It is a vestige of which structure?

$A$: Endocardium provides a smooth lining for the inside of the heart and covers the valves of the heart.
$R$: Endocardium is continuous with the endothelial lining of the large blood vessels associated with the heart and the rest of the cardiovascular system.

Which one of the statements is correct with reference to the circulation of blood in a mammal?

Differentiate between Atrium and Ventricle.

The circulation of blood was discovered by .....