inoculation, in medicine, introduction of a preparation into the tissues or fluids of the body for the purpose of preventing or curing certain diseases. The preparation is usually a weakened culture of the agent causing the disease, as in vaccination against smallpox; however, it may also be composed of antitoxins, which provide immunity themselves, or toxoids, which are proteins that stimulate the body to produce antitoxins (see immunity). Various forms of inoculation were used from ancient times in China, India, and Persia, but it remained for the English physician Edward Jenner in the late 18th cent. to demonstrate its feasibility to the Western world. The term inoculation is used also to refer to the introduction of certain substances into plant tissues or to the placement of microorganisms into culture media (for experimental or diagnostic purposes) or into the soil.