ANTITOXINS 349 



a large spoonful of blood. They are the really important 

 agents in protecting us from microbes, since they not only 

 engulf and digest and so destroy those intruders, but it is 

 probable (not certain) that they also are the manufacturers 

 of the antitoxins and of the germicidal poisons. 



If these three defensive processes given us by Nature 

 are in working order, that is to say, if we are "healthy," 

 they should secure to us a sufficient " immunity " at 

 any rate, " recovery " from any attack of disease-pro- 

 ducing microbes. But they are not in " unselected," widely 

 ranging mankind always equal (in their unaided natural 

 state) to their task. 



The attempts to produce immunity by vaccination with 

 weakened or localised disease germs is really an attempt 

 to train and develop to a high point the activities of the 

 phagocytes or eater-cells of the blood. 



The introduction of antitoxins by injection of them into 

 the blood (as in the treatment of diphtheria, lock-jaw and 

 snake-bite) is an attempt to bring to the rescue of a patient 

 who would sooner or later produce his own antitoxins (but 

 perhaps too late or in insufficient quantity) the similar anti- 

 toxin obtained from the blood of another animal which has 

 been artificially made to produce in its blood an excessive 

 quantity of that substance. 



Mithridates, King of Pontus, was, according to ancient 

 legend, in consequence of his studies and experiments, 

 soaked with all kinds of poisons to which he had become 

 habituated by gradually increasing doses, and he had at 

 last reached a condition in which no poison could harm 

 him, so that when he was captured by the Romans and 

 wished to kill himself (which was the correct thing in 

 those days for a fallen king to do), he wept because he 

 was unable to get any poison which could act upon him. 

 He was " immune " to all poisons. This real or supposed 



