The method of obtaining is similar to that employed for securing the diphtheria antitoxin, the unit, however, being somewhat different. The use of this antitoxin has not been as satisfactory as that of diphtheria, on account of the rapidity with which the central nerve-cells combine with the tetanus toxin and the firmness of that union. Consequently, as a curative after toxic symptoms have developed, it is not very efficient, athough more cases of tetanus do recover after antitoxin treatment than after any other form. Its chief value is as a preventive. It should be given as soon as possible after the injury has been received, in order that the free receptors will be present ready to combine with the toxin as soon as it has formed. By means of this prophylactic dose of antitoxin the number of fatal cases of tetanus infection following injuries received on the 4th of July has decreased very greatly.

Bacterination (bacterial vaccine) refers to the introduction within the body of measured amounts of sterile cultures of bacteria, in order that the individual may develop an immunity to that particular organism. This method has been employed in the infections of many varieties of bacteria, with particularly favorable results where the cocci have been the invaders. In pyorrhea alveolaris much success has been attained.

Two types of bacterins (vaccines) are employed, the stock vaccine and the autogenous vaccine. In the latter the bac-terin is obtained by the cultivation of the organisms present in the lesion of the infected person. The stock vaccine is made of bacteria similar to those in the infected individual, but obtained from some other source. As a rule, better results are obtained by using the autogenous cultures, although in gonococcal infections the stock bacterin seems to be more satisfactory in many instances.