I didn’t know this – until my son told me. From this website.
Sometimes it is necessary for doctors to get access to the heart either for diagnosis or treatment. The simplest way to do this might seem to be to hack open the chest and have a look at the organ itself. Obviously this has massive risks and while even today opening the chest is risky, in the 1930s it would have been almost certainly fatal. Werner Forssman studied corpses and decided it would be possible to pass a thin tube, or catheter, along blood vessels and directly into the heart. Needing to discover whether this would be possible in still living humans he decided an experiment would be in order. He cut open his arm and threaded the tube up and into his heart. A small slip could have torn a major vessel and led to his death but he still needed to prove he had reached the heart. So, with the tube dangling from his arm, he walked from the operating room to an x-ray machine, and took the pictures which showed he had been successful. For this bit of scientific derring-do he shared the Nobel Prize in medicine in 1956.
Naturally two thirds of the current Troppo garage – both the Merc sports and “Rooter” – will be made available over some mutually convenient weekend to any Troppodillian who is able to earn a Nobel Prize in similar fashion.