Dirty forceps. Macrophotograph of surgical forceps with blood or tissue still attached after sterilisation. The forceps were sterilised in an autoclave, a pressurised steam-heated device that heats objects to very high temperatures. This kills virtually all bacteria and viruses. However, some disease vectors, including prions, the infective agent of Creutzfeldt-Jacobs disease (CJD) the human form of mad cow disease, are not destroyed by autoclaving. Dirty surgical instruments could pass on such diseases. Magnification: x4 when printed at 10 centimetres tall.