556 MICROBIOLOGY OF THE DISEASES OF MAN AND ANIMALS. 



infected. The haptophile receptors (antitoxins), after they are thrown 

 off, combine with the toxin haptophore and often the toxophore group 

 does not have the opportunity for combining and killing the cells. This 

 is in case there is no special affinity for the cells, as in the above-mentioned 

 chief antitoxin-producing cells in tetanus. In such cases frequently all 

 the available toxin is bound and very little is left to combine with the tissue 

 with which it has an especial affinity, as is the case with tetanus toxin and 

 nerve tissue. The antitoxins serve in this instance as protective sub- 

 stances. Furthermore, in case the antitoxin is excreted into the blood 

 and lymph, it serves in addition as a curative agent, all the toxin which is 

 produced combining with all the available antitoxin in the circulation, 

 and none is left to combine with the cells of the body. The maximum 

 affinity is always between toxin and antitoxin rather than between toxin 

 and cell, if there is any antitoxin present. Antitoxins are prepared 

 artificially and used for both prophylactic and curative purposes in the 

 treatment and prevention of certain of the infectious diseases such as 

 tetanus and diphtheria. 



Antitoxins are also produced in the bodies of animals which are to all 

 appearances immune to the toxins concerned. For example, the alligator 

 is immune to tetanus, but when tetanus toxin is injected into this animal 

 tetanus antitoxin will be produced. In this case the haptophore group 

 of the toxin has combined with certain of the cells of the body, but with 

 such cells as give no opportunity for the toxophore group to combine, or 

 have no affinity for this group. In the case of the alligator the nerve 

 tissue seems to possess no toxophile receptors for the toxin. 



There are certain animals which are very susceptible to the action of 

 certain toxins which will not produce antitoxin when the toxin is injected. 

 For example, the guinea-pig and the rabbit will not produce tetanus or 

 diphtheria antitoxin when injected with small and gradually increasing 

 doses of tetanus or diphtheria toxin. If the toxin is modified chemically 

 by the addition of chemicals such as trichloride of iodine or by heat, these 

 animals may be immunized and will produce antitoxin. In this instance 

 the virulence of the toxophore group is reduced and it is possible to inject 

 the animals with more toxin, thus combining with more cells and finally 

 liberating more antitoxin. 



It should also be noted that animals of the same species vary in their 

 power to produce antitoxin. The production of the product varies with 

 the age and general condition of the animal and with the duration and the 



