IMMUNITY TO TOXINS 241 



proteolytic enzymes produced by the organisms and as a 

 result of tissue disintegration may have a destructive action 

 on the toxins. Oxidation, hydration and dehydration, 

 and various analytic and synthetic processes which go 

 on in the body, and particularly in the liver, are other 

 agencies whereby toxins may be destroyed. These non- 

 specific processes by which toxin is destroyed or elimi- 

 nated, though of the greatest importance, can probably 

 deal with only small amounts of toxin ; if large amounts 

 are present, specific reactions have to be evoked. 



Another cause of natural immunity to toxins may be 

 the absence of suitable receptors for the toxin. As already 

 stated (p. 182), in order that a bacterial toxin or endotoxin 

 may produce intoxication, it must become anchored to 

 the cells by its haptophore group, and that this may 

 occur the cell molecules must possess receptor groups 

 which have a special affinity for the haptophore groups 

 of the toxin. Should these be wanting the toxin cannot 

 become anchored to the cells, its toxophore groups cannot 

 exert their influence, and natural immunity is the result. 



This has been proved to be the case in several instances. 

 Thus in the lizard and turtle, if tetanus toxin be injected 

 no effect is produced, but the toxin is not eliminated and 

 remains in the body for months, as may be proved by 

 withdrawing a little of the blood and injecting it into a 

 mouse ; the animal dies of tetanus. 



In other instances, for some reason or other, the cells 

 of the animal are insusceptible to the toxophore group of 

 the toxin. Thus, if an alligator be injected with tetanus 

 toxin, no effect is produced, but the toxin rapidly dis- 

 appears from the blood. If the animal be kept at ordinary 

 temperature (20 C.), although the toxin disappears, 

 antitoxin is not formed, but if it is kept at 30-37 C. anti- 

 toxin is rapidly produced. The two experiments together 

 suggest that the toxin is fixed by the cells, but has no 



M.B. 16 



