566 BACTERIOLOGY. 



above, in hypercompensation, the excess of plastic mate- 

 rial being disengaged from the parent-cell and thrown 

 free into the circulating fluids, there to combine directly 

 with the same intoxicant should it subsequently gain 

 access to the animal. This excess of plastic material 

 thrown into the circulation combines, according to Ehr- 

 lich,^ directly with the intoxicant to form physiologic- 

 ally inactive toxin — antitoxin comjjounds (see page 497), 

 and can therefore be reasonably regarded as the antitoxic 

 material of animals immune from bacterial and other 

 toxins. Since the announcement of that doctrine many 

 important advances have been made in our knowledge of 

 the subject. We have learned that immunity or tolerance 

 may be induced by the use of other intoxicants than those 

 elaborated by bacteria, and by the employment of other 

 cells and cell secretions. It has been demonstrated that 

 anti-bodies, diifering in their specific actions from anti- 

 toxins, but originating probably in a similar manner, are 

 to be detected in the fluids of animals thus immunized or 

 rendered tolerant. For a long time we have known of 

 the germicidal action of normal blood-serum ; for several 

 years we have been familiar with the singular bacterio- 

 lytic phenomenon demonstrated by Pfeiffer in the peri- 

 toneum of animals immune of cholera ; more recently 

 we have learned that immunity from a variety of infec- 

 tions is accompanied by a power on the part of the 

 serum of the immune animal to agglutinate the bacteria 

 causing the infection ; and the profoundly interesting 

 investigations of Bordet, INIoxtcr, von Dungern, Fish, 

 and others, have shown that immunity may be induced 

 from cells and secretions of animal origin hitherto re- 



1 Ehrlich : " Zur Keniitniss der Antitoxinwirkiing," Fortschritte der 

 Medicin, X897, Bd. xv, Wo, ?, 



