IMMUNITY AND SUSCEPTIBILITY 701 



toxin, also produce antitoxin. For example, tetanus toxin has an 

 especial affinity for nerve tissue but this tissue produces little of the 

 antitoxin. In this case most of the antitoxin seems to be produced in 

 the spleen, lymph glands and bone marrow. The haptophore groups 

 of the toxin have at least combined with these cells and stimulated them 

 to the overproduction of haptophile receptors. 



It has been mentioned that the antitoxins are protective to the body 

 infected. The haptophile receptors (antitoxins) before they are thrown 

 off combine with the toxin-hap tophore 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-men- 

 tioned chief antitoxin-producing cells in tetanus. In such cases fre- 

 quently 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 substances. Furthermore, in case the antitoxin is ex- 

 creted into the blood and lymph it serves in addition as a curative agent, 

 all the toxin which is produced combining with all the available anti- 

 toxin in the circulation and none is left to combine with the cells of 

 the body. The maximum affinity is always between toxin and anti- 

 toxin rather than between toxin and cell, if there is any antitoxin 

 present. Antitoxins are prepared artificially and used for both pro- 

 phylactic 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 hapto- 

 phore 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 chemical receptors for 

 the toxin. 



There are certain animals which are very susceptible to the action 

 of certain toxins and 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 



