282 BACTERIOLOGY 



of these conditions of immunity or tolerance above noted 

 antitoxins, as we know them, are not present at all. 



In an important series of papers on the hemolysins pub- 

 lished by Ehrlich and Morgenroth' an effort is made to 

 elucidate further the finer mechanism of immunity in its 

 broad sense and various expressions, and to adapt the side- 

 chain doctrine to those more complicated phenomena in 

 which immunity depends not only on the elaboration of 

 antitoxins, but also upon a power on the part of the animal 

 fluids to cause a complete metamorphosis or disappearance 

 of such particulate matters as bacterial and other irritating 

 or poisonous cells and substances. They believe the forces 

 at work in the establishment of immunity from bacteria 

 and from bacterial and other toxins, those operative in the 

 elaboration of the newly discovered lysins, antilysins, 

 agglutinins, precipitins, ferments, antiferments, etc., as 

 well as those concerned in physiological assimilation and 

 nutrition, to be fundamentally identical. They believe 

 susceptibility to infection, as well as power to assimilate 

 nutrition, to be explainable through the assumption that 

 special molecular groups of the living protoplasm are endowed 

 with specific combining affinities for particular matters; and 

 in so far as the establishment of disease is concerned, they 

 regard the receptivity of the individual to be determined 

 entirely by the greater or less susceptibility of those pro- 

 toplasmic molecular groups — "receptors," as they designate 

 them — to disease-producing agents. In individuals that 

 have been artificially immunized from hurtful substances 

 they believe (in reiteration of Ehrlich's view expressed 



1 Berliner klinische Woohensohrift, 1899, Bd. xxxvi, S. 6 and 481; 1900, 

 Bd. xxxvii, S. 458 and 681; 1901, Bd. xxxviii, S. 251, 569, 598. See also 

 Schlussbetrachtung: Ehrlich in Nothnagel'a Speciellen Pathologic und 

 Therapic, Bd. vii, Theil 1, Heft 3, S. 161. 



