Immunity against toxins also became a subject of investigation, and the result was the discovery of the antitoxic action of the serum of animals immunized against tetanus toxin by E.
The term " antitoxic " signifies that serum has the power of neutralizing the action of the toxin, as is shown by mixing them together outside the body and then injecting them into an animal.
The antitoxic serum when injected enttinoxic previously to the toxin also confers immunity (passive) against it; when injected after the toxin it has within certain limits a curative action, though in this case its dose requires to be large.
The antitoxic property is developed in a susceptible animal by successive and gradually increasing doses of the toxin.
An antitoxic serum has been prepared from horses by the Institut Pasteur in France, but has not met with success.