PRACTICAL METHODS IN IMMUNITY 



resistance of bacteria that the phagocytes ingest them. By bacterio- 

 lytic power 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. 



Of the different kinds of immunity only artificial immunity will be considered. 

 This may be obtained in two ways: 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 (antitoxins) or bring about lysis 



of the specific bacteria (bacterioly- 

 sins). These antibodies which are 

 supposed to be thrown off (free re- 

 ceptors) 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 en- 

 during 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 repro- 

 duced in great excess by nature. 



Not only may bacteria act 

 in this way but foreign cells, 

 such as red cells or various 

 parenchymatous cells, when in- 

 jected, give rise to antagonistic 

 substances which act as factors in 

 their destruction haemolysins 

 for red cells, cytolysins for dif- 

 substance which is injected and 

 produced is called an antigen. 



FIG. 44. Receptors of the first order 

 uniting with toxin. (Journal of the A merican 

 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. 



feient parenchymatous cells. The 

 in reaction to which antibodies are 

 This is termed "active immunity." 



When we take the serum of a man or animal immunized actively and inject 

 it with its contained antibodies into a second animal or man, we confer an immunity 

 on the second animal; but as his cells take no active part in the production of the 

 immunity, but are only passive, we term this immunity "passive immunity." If 

 this serum which is introduced in passive immunity only neutralizes the toxic prod- 

 ucts 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 anti- 



