One of the first major discoveries relevant to the field of appendix, hernia, keyhole surgery was the discovery of pulmonary circulation. Originally, it was thought that blood reaching the right side of the heart passed through small ‘pores’ in the septum into the left side to be oxygenated, as theorized by Galen; however, the discovery of pulmonary circulation disproves this theory, which had previously been accepted since the 2nd century. Thirteenth century anatomist and physiologist Ibn Al-Nafis accurately theorized that there was no ‘direct’ passage between the two sides.