The study of the circulation by cardiac catheterisation started in 1844 when Claude Bernard performed retrograde left and right heart catheterisation, from the jugular vein and carotid artery, in a horse. Application of these principles and techniques in patients was made possible by the discovery of X-rays by William Conrad Roentgen (1845–1923) on November 8, 1895, at the University of Wurzburg. He received the Nobel Prize for his discovery in 1901. Roentgen’s discovery enabled Werner Forssmann to perform the first cardiac catheterisation on himself under fluoroscopic guidance in 1929 in a small hospital in Eberswald in Germany. He passed a urethral catheter from an arm vein into his right heart. To do this he needed the co-operation of a surgical nurse whom he persuaded to help against the orders of his hospital chief. Forssmann wrote of his findings in 1929 (Forssman 1929); however, the medical establishment failed to recognise his findings. He gave up his work and continued training as a urological surgeon.