162 



PRACTICAL METHODS IN IMMUNITY 



together and form clumps. By precipitating power we mean the 

 ability of such a serum to cause precipitates in a clear bouillon filtrate 

 of the specific bacterium. Such antibodies are called precipitins or 

 coagulins. Bfv^/psonic power we mean that antibody which so alters 

 tne resistance of bacteria that the phagocytes ingest them. By^pac- 

 teriolytic poj^er we mean that which brings about disintegration or lysis 

 of the specific organism. The bacterium which causes the disease or 

 which is used in inoculation for the production of immunity is termed 

 the specific organism. 



FIG. 45. Receptors of the first order uniting" with toxin. (Journal of the Ameri- 

 can Medical Association, 1905, p. 955.) a, Cell receptor; b, toxin molecule;^ c , 

 haptophore of the toxin molecule; d, toxophore of the toxin molecule; e, haptophore 

 of the cell receptor. 



Artificially Acquired Immunity. Of the different kinds of immunity only artificial 

 immunity will be considered. This may be obtained in two ways : i. By injecting 

 the bacteria or their products into man or animals and as the result of the activity of 

 the cells of the animal invaded, antibodies' are formed which neutralize the toxins 

 (anj^tp^is) or bring about lysis W Ine specific bacteria (baclmojysins). These 

 antibodies which are supposed to be thrown off (free receptors) from those body cells 

 which have suitable fixation powers for the invading toxin molecule or bacterium 

 may remain potential for months or years and so confer a more or less enduring 

 immunity. 



These fixation points are known as cell receptors and are intended for 

 the assimilation of various foodstuffs by the cell. If destroyed by the 

 toxin or bacterium they are reproduced in great excess by nature. 



