MASTERING THE MICROBE 



acteristic ways. These substances are so-called (1) 

 anti-toxines that neutralize the bacterial poison; (2) 

 bactericides that tend to kill the bacterium; (3) 

 bacteriolysins that tend to dissolve it; (4) agglutinins 

 that interfere with its activities; and (5) opsonins 

 that make it an easy prey for the white blood cor- 

 puscles that constitute Nature's body guard of 

 soldiers everywhere patrolling the blood. 



These" "anti-bodies," various and sundry, are so 

 intangible that the chemist cannot as yet analyze 

 them. Yet they make their presence felt by very 

 definite results. A different set of these antidotes 

 is produced in opposition to each particular kind of 

 noxious microbe. If the tissues are able to produce 

 them fast enough in any given case, the invading 

 microbes are destroyed, and disease is warded off. 

 If, on the other hand, the invaders come in too great 

 numbers, or multiply too rapidly, the antidotes can- 

 not cope with them, and the disease develops. 



Now the dead germs that the inoculator introduces 

 in producing artificial immunity carry with them a 

 certain increment of poison, and excite the tissues 

 to production of antidotes precisely as would living 

 microbes. There is, however, the important differ- 

 ence that the dead microbes obviously cannot multi- 

 ply and so overwhelm their host with the power of 

 numbers. The number of microbes and therefore the 

 quantity of poison introduced can be graduated at 

 will of the inoculator, who is careful to introduce 

 only such numbers as experience has shown will not 

 produce too powerful an effect. 



So the tissues are able to manufacture sufficient 



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