168 ACTIVE IMMUNIZATION 



received no human serum, but which had otherwise been treated 

 in the same manner lived. Evidently a lack of complement in the 

 course of an infection may lead to disastrous consequences, and the 

 assumption seems justifiable that the presence of an insufficient 

 quantity at the start may favor the generalization of an infection 

 where otherwise a local reaction only might have taken place. 



That the normal amboceptors might be similarly influenced is, of 

 course, also possible, and is suggested by certain experiments of Abbot 

 and Bergey, who found that the hemolytic amboceptors which 

 appear in the guinea-pig following the injection of alien red corpuscles 

 rapidly disappear under the continued administration of alcohol. 



These data, few as they are, throw some light upon the possible 

 modus operandi of some of the causes which predispose to infectious 

 diseases, and open up a field for investigation which, speaking 

 a priori, should furnish some very valuable results. Studies in this 

 direction would also show by what general non-specific measures, 

 dietetic, medicinal, or otherwise, the resistance against infection 

 could be raised, and the likelihood of successful specific treatment 

 thereby enhanced. At the present time the latter occupies the fore- 

 ground of medical interest, and it is the purpose of the following 

 pages to show what has already been accomplished, both from the 

 standpoint of prophylaxis and of treatment. 



In arranging the sequence of our subject matter, precedence is 

 given to those methods by which immunity can be actively produced, 

 for here the entire defensive mechanism is thrown into operation, 

 whereas in the production of passive immunity only certain indi- 

 vidual defensive principles are utilized. 



(A) ACTIVE IMMUNIZATION FOR PROPHYLACTIC PURPOSES 



Since the entire defensive mechanism of the animal body is thrown 

 into action as a result of active immunization it would suggest itself 

 that attempts in this direction would furnish the most valuable 

 results when employed for prophylactic purposes. When infection 

 has once taken place, and clinical symptoms of disease have already 

 developed, conditions are much more complicated. The effect of 

 toxins, whether produced by the infecting organisms themselves, or 

 as a result of anaphylactic reaction, then so frequently dominates 



