IMMUNITY 17 



other atom groups or ** side-chains " of the proto- 

 plasm of the tissue cell. These "side-chains" or 

 receptors, then, reproduced in excess and finally 

 thrown free into the circulation, constituted the 

 immune bod3\ 



Ehrlich concludes that in the case of hemolysis 

 complement does not combine directly with the cor- 

 puscles, but does so through the intervention of the 

 immune body. This immune body, he reasons, pos- 

 sessed two distinct atom groups or haptophores : one, 

 the cytophile haptophore group, with strong affinity for 

 red blood cells; the other, or complementophile hapto- 

 phore group, with weaker affinity for the complement. 

 Because of this double combining power he speaks of 

 the immune body as " amboceptor." 



Agrgrlutinins.— As has already been mentioned, 

 immune serum has the property of agglutinating 

 bacteria, and as this property is specific for the 

 bacteria which produced the immunity, especially 

 when an emulsion of high dilution of the bacteria is 

 made, this fact is taken advantage of for bacterial 

 species differentiation in clinical diagnosis. Widal's 

 test for typhoid is an application of this agglutination 

 phenomenon ; and this test is of great importance, as 

 the serum of patients suffering from this disease 

 shows agglutinating power over the typhoid bacillus 

 at early stages in the course of enteric fever. 



Production of Ag'g'lutinins. — Just as normal 

 serum contains small quantities of bactericidal sub- 

 stances, so does it contain agglutinins in small 



2 



