""" In 1929, while working in Eberswalde, he performed the first human cardiac catheterisation. He ignored his department chief and persuaded the operating-room nurse in charge of the sterile supplies, Gerda Ditzen, to assist him. She agreed, but only on the promise that he would do it on her rather than on himself. However, Forssmann tricked her by restraining her to the operating table and pretending to locally anaesthetise and cut her arm whilst actually doing it on himself.[3] He anesthetized his own lower arm in the cubital region and inserted a uretic catheter into his antecubital vein, threading it partly along before releasing Ditzen (who at this point realised the catheter was not in her arm) and telling her to call the X-ray department. They walked some distance to the X-ray department on the floor below where under the guidance of a fluoroscope he advanced the catheter the full 60 cm into his right ventricular cavity. This was then recorded on X-Ray film showing the catheter lying in his right atrium. """ https://en.wikipedia.org/wiki/Werner_Forssmann#Life

In home fermenting, you have living lactic acid bacteria of various kinds, and they out-compete the bad bacteria. You may help them along with some salt and acid. In home canning, you kill most of the living bacteria in the sample and seal it. If you get the acidity wrong, clostridium and other spores then come to life and poison your food product. They can do this easily, because there's nothing to compete with them and because the environment is anaerobic. Safe canning requires other specific acidity and salinity, or pressure canning at a high enough temperature to kill bacterial spores.

If you follow some basic rules about salinity and only ferment raw vegetables, the practice is very safe. Half-ass canning, on the other hand, or mess with cooked foods and meats, and you're walking a dangerous line.