DEFLECTION OF COMPLEMENT 213 



thought-out experiments, believes that the phenomenon is 

 brought about by the presence of inhibiting bodies which must 

 be regarded as specific an ti- bodies which combine with dissolved 

 antigen to form complexes which have a marked tendency to 

 absorb complement and to withdraw it from bactericidal anti- 

 bodies, i.e. they function as an ti -complement. 



Aggressins 



Bail has discussed the question of the relationship between 

 bacteriolysis and immunity. He argues that there is apparently 

 little relationship between the bactericidal properties of the body 

 fluids and the immunity of an animal to infection through bacterio- 

 lytic processes ; and points out that in rabbits immunised against 

 anthrax there is no bacteriolytic power, the bacteria disappearing 

 gradually as the result of phagocytic action of cells, chiefly mar- 

 row-cells ; that a comparison of the sera of sheep, rabbits, and 

 cattle shows great variation in their content of immune body, 

 though the animals are almost equally susceptible to anthrax ; and 

 that in test-tube experiments a bacteriolytic serum is blocked 

 when the conditions are approximated to those in the body by 

 the addition of body cells to the mixture ; the bactericidal pro- 

 perties of the serum disappear or are greatly inhibited. Kruse 

 suggested that for infection to take place the invading bacteria 

 must elaborate chemical substances which so act on the cells and 

 fluids of the invaded animal that they overcome its natural resis- 

 tance against infection. These substances are considered by him 

 and Bail to be distinct from the toxins, and are termed by these 

 writers " aggressins." l The aggressins are supposed to be 

 secreted by the living uninjured bacteria and not to be extracts, 

 nor derived by solution, of the bacteria ; they occur particularly 

 in the fluids of pathological oedemas and exudates, and may be 

 obtained from these by centrifugation and sterilisation at low 

 temperatures. Bail believes that the aggressins cannot be anti- 

 complements, anti-immune bodies, etc., but are substances hereto- 

 fore unrecognised and the active substances of the infection, 



i See Centr. /. BaJct., Orig., xlii, 1906, pp. 51, 139, 241, 335, 437, and 546 ; 

 also an excellent summary by Marshall, Philippine Journ. of Science, vol. ii, 

 1907, p. 352. 



