IMMUNITY 197 



1. Natural immunity against toxins. There are various 

 non-specific reactions in the body by which toxins may 

 be eliminated or destroyed. Thus the dilatation of the 

 vessels and the acceleration of the blood-stream which 

 take place in an inflamed area dilute and eliminate the 

 toxin, and the 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 particu- 

 larly in the liver, are other agencies whereby toxins may be 

 destroyed. These non-specific processes by which toxin 

 is destroyed or eliminated, though of the greatest impor- 

 tance, 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. 153), 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 atomic groups or side- 

 chains (" 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 



