128 BACTERIOLOGY FOR NURSES 



bacilli or their products cause the production of an antibody of 

 this nature, so that when the serum of a typhoid patient is mixed 

 with its antigen, typhoid bacilli, the latter lose their motility and 

 become clumped together in masses. The other antibody of this 

 class appears to coagulate and precipitate soluble substances and 

 accordingly is known as precipitin. Such protein substances as 

 milk, egg albumen, etc., will if injected into an animal cause the 

 production of precipitin. 



Third Order (Bacteriolysins, Hemolysins, Cytolysins). For 

 still more complex food molecules that require converting into 

 simpler substance before they can be assimilated Ehrlich con- 

 ceived a third order of receptors or side chains. These he assumed 

 to be composed of two haptophore or grasping portions, one for 

 union with the food molecule and the second for union with a 

 special ferment-like substance normally present in the blood 

 and called by him " complement " ; by French writers the same 

 substance is referred to as " alexin " or " cytase." The receptors 

 therefore act simply as a connecting link or interbody between 

 the food and the complement, serving to bring them in relation 

 with each other. This union renders the food molecule soluble. 

 In other words, it undergoes lysis. 



Hemolysins, bacteriolysins, and cytolysins are the antibodies 

 of this order. If, for example, the red blood cells of one animal 

 are injected into another species they combine with the receptors 

 of the third order attached to the cell. As they are toxic the result 

 is the formation of antibodies (hemolysins) . If more of the anti- 

 gen, which in this case is the foreign corpuscles, be injected, the 

 hemolysins uniting them with the complement in the blood cause 

 them to be completely dissolved. If certain bacteria are injected 

 into an animal immunized against that particular species, conse- 

 quently in whose blood bacteriolysins are circulating, they share 

 the same fate as the corpuscles in the previous example. Thus 

 the production of bacteriolysins offers a satisfactory explanation 

 of " Pfeiffer's phenomenon." It should be remembered that 

 although these antibodies prepare their antigens for lysis, or " sen- 

 sitize" them, they are not in themselves lytic, final solution of the 



