Vein they were for transport of air. The Greek physician, Herophilus, distinguished veins from arteries but thought that the pulse was a property of arteries themselves. Greek anatomist Erasistratus observed that arteries that were cut during life bleed. He ascribed the fact to the phenomenon that air escaping from an artery is replaced with blood that entered by very small vessels between veins and arteries. Thus he apparently postulated capillaries but with reversed flow of blood. 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)
Anterior spinal veins infiltrate back into the ventral median spinal fissure previously mentioned by up to a few centimeters. They are also not only smaller in size but more numerous than the equivalent anterior spinal artery which they lie dorsal to. There are three anterior spinal veins in total. These, along with three posterior spinal veins, are allowed to communicate with one another as they run interconnected throughout the entire length of the spinal cord. This is seen through both sets of veins combining to form a network of anastomoses around the conus medullaris. Together, these two sets of veins also collect blood