120 



PRACTICAL METHODS IN IMMUNITY. 



disintegration or lysis of the specific organism. The bacterium 

 which causes the disease or which is used in inoculation for the pro- 

 duction of immunity is termed the specific organism. 



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 of 

 or destroy the specific bac- 

 teria. These antibodies which 

 are supposed to be thrown off 

 (free receptors) or which may 

 remain attached to the cell 

 (sessile receptors) may re- 

 main potential for months or 

 years and so confer a more 

 or less enduring immunity. 

 This is termed active im- 

 munity. 2. When we take 

 the serum of a man or animal 

 immunized actively and inject 

 it with its contained anti- 

 bodies into a second animal 

 or man, we confer an im- 

 munity on the second animal; 

 but as his cells take no active 

 part in the production of the 

 immunity, but are only pas- 

 sive, we term this immunity " passive immunity." If this serum which 

 is introduced in passive immunity only neutralizes the toxic products 

 of the infecting bacteria, we term it antitoxic passive immunity and 

 designate the immune serum as antitoxic serum. If it destroys the 

 organism, we call it antimicrobic serum, and the immunity, antimi- 

 crobic passive immunity. Some immune sera are both antitoxic and 

 antimicrobic. 



It is well to remember that some organisms produce a toxin which 



FIG. 44. Receptors of the first order uniting 

 with toxin. (Journal oj the American Medi- 

 cal Association. 1905. P. 955.) 



a, Cell receptor; 6, toxin molecule; c, hap- 

 tophore of the toxin molecule; d, toxophore 

 of the toxin molecule; e, haptophore of the 

 cell receptor. 



