72 CLINICAL BACTERIOLOGY. 



onstration was first made experimentally for pneumonia, 

 later for typhoid fever, diphtheria, and cholera, that the 

 blood of individuals convalescent from these diseases ex- 

 hibits in many instances transitory immunizing activities 

 with relation to the respective bacteria. It appears from 

 this as if recovery from these diseases also is attended with 

 immunity, but that this through causes not yet made 

 clear is a quickly passing one. 



It has been demonstrated experimentally with certainty 

 that immunization may also lead to cure. By means of 

 serum-immunization it is possible, if the serum is derived 

 from animals highly enough immunized, to induce curative 

 results, even when the treatment is begun a certain time 

 after infection has taken place. These facts are most con- 

 clusively demonstrable experimentally in the case of tetanus. 

 With large amounts of serum from animals immunized to 

 tetanus, it is possible to save mice and guinea-pigs that 

 already exhibit distinct tetanic manifestations. We shall 

 refer more fully to these relations in the special section. 

 (See Diphtheria and Tetanus.) 



According*to the foregoing, two facts have been demon- 

 strated in the first place, that immunity exists at the time 

 of recovery in the sequence of toxic diseases in man, and, in 

 the second place, that it is possible experimentally to cure 

 infection by the timely establishment of immunity. From 

 this the conclusion may, with all probability, be drawn that 

 also in human beings the connection between recovery and 

 immunity consists in the bringing about of recovery through 

 the development of immunity ; recovery from the given 

 disease immunizes the organism, and cure is effected in 

 consequence of immunization naturally induced, and espe- 

 cially the crisis appears as the expression of cure through 

 the sudden setting in of immunity. Upon this knowledge 

 is based recent therapeutic effort, which is known as 

 serum-therapy or immunization-therapy. The object to be 

 attained is the immunization of the diseased organism after 

 infection has taken place that is, the effecting of a cure in 

 the same way as nature brings about recovery in cases of 

 infectious disease pursuing a favorable course. This mode 

 of therapy is naturally specific, as immunity also is specific. 

 Much more serum, however, is required to effect a cure 

 than to induce immunity ; or, what amounts to the same 

 thing, the serum of much more highly immunized animals. 



