456 H^EMOLYSINS AND ALLIED BODIES 



we shall study presently. Before doing so, however, another 

 property of many of these substances, viz. their power of producing 

 agglutination of the red corpuscles, must be studied. This frequently 

 goes hand in hand with hsemolysis, although we have reason for 

 believing that the two processes are produced by entirely different 

 agencies. Bordet first discovered that the serum of an animal 



A, which has been gradually injected with the blood of an animal 



B, when added to some defibrinated blood of B, caused an 

 immediate agglutination of the corpuscles, so that clumps of them, 

 suspended in the serum, were formed. This clumping is very 

 evident on shaking the test-tube. Other signs of agglutination are 

 the rapidity with which the clumped corpuscles settle down, and 

 the fact that, on filtering the blood through paper, the corpuscles 

 remain behind as a precipitate, whereas in normal blood they filter 

 through. 



These haemagglutinins are analogous with bacterioagglutinins, 

 discovered by Gruber, Durham, and Widal in the blood serum of 

 animals injected with certain organisms ; for example, the serum 

 of a typhoid patient agglutinates typhoid bacilli. With regard to 

 their mode of action, it is necessary to somewhat modify the side- 

 chain theory as applied to the process of hsemolysis. The re- 

 ceptor which produces the clumping is supposed to be furnished 

 at one end with a functionating or agglutinophoric group, the 

 other end being a haptophoric or combining group. This latter, 

 when agglutination occurs, is supposed to anchor on to a suitable 

 receptor of the erythrocyte or bacterium. When thus united, the 

 agglutinophoric end of the agglutinin amboceptor acts in some, not 

 yet clearly described, manner on the cell, whereby it causes these 

 cells to clump together. Such receptors Ehrlich called receptors of 

 the second order, and the essential difference between them and 

 hsemolysin receptors (i.e. third order) is that the complemento-philic 

 group is replaced by a zymophoric or acting group, which does not 

 require to become combined with complements before it can act. 



These agglutinins are quite distinct from haemolysins or 

 bacteriolysins, although some observers have thought them to be 

 identical. Thus Gruber thinks agglutination to be the preliminary 

 stage of bacteriolysis, and Baumgarten thinks the agglutinin to be 

 the same thing as the amboceptor, the apparent difference between 

 them being, according to this observer, merely a quantitative one. 



That the two are different processes, however, is shown by the 

 following facts: (1) agglutinated bacteria can multiply as well as can 



