482 MICROBIOLOGY 



groups have the greater variety of functions, especially those 

 of nutrition and assimilation. This theory teaches that im- 

 munity depends upon the presence or absence of certain sub- 

 stances which he calls receptors or lateral chains which certain 

 of the cells possess. These receptors are concerned in the 

 normal nutrition of the cells and have affinities for various 

 complex albuminous substances. Among these substances are 

 the molecules of the toxin produced by certain bacteria and 

 possibly other poisons. Every toxin has affinities described 

 as haptophorous and toxophorous. that is, every molecule of 

 the toxin is composed of two different groups of atoms, the one 

 the toxophore or poisonous group, the other the haptophore, or 

 combining group of atoms. The haptophorous molecules of the 

 toxin combine or unite with the receptors of those cells for 

 which they have special affinity and through the haptophore 

 group the toxophore part of the molecule is able to act upon 

 the cell. In some cases the cells are destroyed and in others 

 additional receptors seem to be produced because of the stimu- 

 lation. These receptors may pass out of the cell into the serum, 

 where they act as free receptors or immune bodies to lock up 

 or neutralize the toxin. The free receptors are the active part 

 of the antitoxin. 



Toxic and bacterial immunity. Investigations have 

 shown that there are two distinct types of acquired immunity 

 against bacterial diseases, namely : (1) toxic immunity and (2) 

 bacterial immunity. Toxic immunity is where the disease is 

 caused by the elaboration of an extracellular toxin such as, 

 exists in diphtheria and tetanus and where the individual is 

 immunized either by the production of an antitoxin within 

 the body due to an attack of the disease or where the antitoxin 

 has been injected into the body. Bacterial immunity is where 

 amboceptors or immune bodies are present, having been pro- 

 duced in the body by the infecting organisms (Pfeiffer's 

 phenomenon), or introduced from without. Toxic immunity is 

 easily acquired against the toxic diseases such as diphtheria 

 and tetanus but the production of bacterial immunity against 

 the diseases in which the bacteria destroy the tissues such as 



