420 APPLICATION OF METHODS OF BACTERIOLOGY 



We see then that while active immunization is compara- 

 tively easy of accomplishment, the matter is altogether 

 different when the serum of animals so immunized is used 

 for therapeutic purposes. The failure of serum from im- 

 munized animals to assist in the cure of pneumonia or 

 other pneumococcus infection with certainty is variously 

 explained, but as yet none of the explanations are univer- 

 sally accepted. By some it is believed that immune serum 

 has not been used in sufficient quantities; by others it is 

 believed that if the intensity of the infection exceeds a 

 certain degree that no amount of immune serum will suffice 

 to rescue. This latter view is particularly applicable to 

 pneumonia, a disease in which one is dealing with an unusu- 

 ally severe type of infection associated with enormous 

 numbers of bacteria in the body. 



Cole suggests that the failure of immune serum to exhibit 

 its curative powers in the cure of pneumonia may not be 

 due to too small amounts of serum used, but rather to an 

 inability on the part of the infected body to supply the 

 factors necessary to complement the action of the serum. 

 His investigations lead him to several important conclu- 

 sions, among which may be mentioned: Since pneumococci 

 may be divided into several distinct groups, it is necessary 

 to use for curative purposes a serum from an animal immu- 

 nized from a strain of pneumococci belonging to the same 

 group as that with which the patient is infected. In order 

 to be effective antipneumococcus serum must be adminis- 

 tered early and in large doses. With these facts in mind the 

 treatment of human beings suffering from pneumonia with 

 homologous, immune serum has resulted in very low mor- 

 tality. In cases so treated the bacteria in the blood are 

 destroyed and specific immune substances appear in the 



