﻿352 MARSHALL. 



II. THE AGGRESSIN HYPOTHESIS. 



Bail's studies in infection and immunity convinced him that bacterio- 

 lysis has little or nothing to do with true immunity against disease and 

 that Ehrlich and his school have followed the wrong clue. He brings 

 forward the following facts in support of this contention : , 



(a) A rabbit is susceptible to anthrax, although its serum is lytic for 

 the germ, while the naturally immune fowl has a serum which is not 

 lytic. 6 



(b) In rabbits immunized against anthrax, and in those passively 

 immunized, there is no bacteriolytic power. Bacteria disappear grad- 

 ually as the result of the phagocytic action of cells, chiefly marrow cells, 

 but do not disappear suddenly because of lysis. 



Sobernheim found that animals upon which he conferred a high 

 immunity against anthrax exhibited no agglutinating action and no 

 lytic action, whereas his guinea pigs, immunized with the anthrax 

 bacilli which had been grown at high temperatures or killed, exhibited 

 no true immunity, but a rich content in immune bodies, the richest 

 anti-body serums, however, affording no true immunity. Bail found 

 similar but not identical, relations to hold with typhoid. 



(c) A comparison of the sera of sheep, rabbits and cattle shows 

 great variations in the amount of immune bodies contained, while these 

 animals are nearly equally susceptible to anthrax. 



(d) In test-tube experiments, a bacteriolytic serum is blocked when 

 the conditions are approximated to those in the body by adding body 

 cells to the fluid. 



(e) Evidence is furnished (Hoke) that what has been said of anthrax 

 holds for other organisms. 



(f) Bail concluded from his studies that animals which survive the 

 Pfeiffer test owe their lives not to bacteriolysis, but to active phagocytosis. 

 He considers that the virulence of bacteria depends not upon toxin pro- 

 duction, but upon the power of the bacteria to multiply in the infected 

 body. He shows that after intravenous inoculations of animals, one 

 with anthrax, the other with hay bacillus, the early reactions are the 

 same in the two animals, the difference appearing only when anthrax 

 begins' to multiply, and even very shortly before death the organs of the 

 anthrax animal are sterile. 



He then seeks to explain the fact that a very small number of patho- 

 genic bacteria may manage to obtain a foothold in the infected body and 

 survive the attacks of the agencies protecting their host. He assumes 

 that the protective body-forces are interfered with in some way, at first 



For other examples of this condition see Deutseh and Feistmantel. 



