<P> In 2nd century AD Rome, the Greek physician Galen knew that blood vessels carried blood and identified venous (dark red) and arterial (brighter and thinner) blood, each with distinct and separate functions . Growth and energy were derived from venous blood created in the liver from chyle, while arterial blood gave vitality by containing pneuma (air) and originated in the heart . Blood flowed from both creating organs to all parts of the body where it was consumed and there was no return of blood to the heart or liver . The heart did not pump blood around, the heart's motion sucked blood in during diastole and the blood moved by the pulsation of the arteries themselves . </P> <P> Galen believed that the arterial blood was created by venous blood passing from the left ventricle to the right by passing through' pores' in the interventricular septum, air passed from the lungs via the pulmonary artery to the left side of the heart . As the arterial blood was created' sooty' vapors were created and passed to the lungs also via the pulmonary artery to be exhaled . </P> <P> In 1025, The Canon of Medicine by the Persian physician, Avicenna, "erroneously accepted the Greek notion regarding the existence of a hole in the ventricular septum by which the blood traveled between the ventricles ." While also refining Galen's erroneous theory of the pulse, Avicenna provided the first correct explanation of pulsation: "Every beat of the pulse comprises two movements and two pauses . Thus, expansion: pause: contraction: pause . (...) The pulse is a movement in the heart and arteries...which takes the form of alternate expansion and contraction ." </P> <P> In 1242, the Arabian physician, Ibn al - Nafis, became the first person to accurately describe the process of pulmonary circulation, for which he has been described as the Arab Father of Circulation . Ibn al - Nafis stated in his Commentary on Anatomy in Avicenna's Canon: </P>

Where is the veins located in the human body