问题描述：
Unlike chemists and physicists，who usually do their experiments using machines，biologists and medical researchers have to use living things like rats．But there are three Nobel prize-winning scientists who actually chose to experiment on themselves-all in the name of science，reported The Telegraph．
●Werner Forssmann （Nobel prize winner in 1956）
Forssmann was a German scientist．He studied how to put a pipe inside the heart to measure the pressure inside and decide whether a patient needs surgery （手术）．
Experiments had been done on horses before，so he wanted to try with human patients．But it was not permitted because the experiment was considered too dangerous．
Not giving up，Forssmann decided to experiment on himself．He anaesthetized （麻醉） his own arm and made a cut，putting the pipe 30centimeters into his vein （血管）．He then climbed two floors to the X-ray room before pushing the pipe all the way into his heart．
●Barry Marshall （Nobel prize winner in 2005）
Most doctors in the mid-20th century believed thatgastritiswas down to stress，spicy food or an unusually large amount of stomach acid （胃酸）．But in 1979an Australian scientist named Robin Warren found that the disease might be related to a bacteria （细菌） called Helicobacter pylori．So he teamed up with his colleague，Barry Marshall，to continue the study．When their request to experiment on patients was denied，Marshall bravely drank some of the bacteria．Five days later，he lost his appetite and soon was vomiting （呕吐） each morning-he indeed had gastritis．
●Ralph Steinman （Nobel prize winner in 2011）
This Canadian scientist discovered a new type of immune system cell （免疫细胞） called the dendritic cell．He believed that it had the ability to fight against cancer．
Steinman knew he couldn't yet use his method to treat patients．So in 2007，when doctors told him that he had cancer and that it was unlikely for him to live longer than a year，he saw an oppor
