MASTERING THE MICROBE 



important test in the course of their experiments with 

 typhoid. The discovery placed in their hands for the 

 first time a method of accurately testing the response 

 which the tissues of the body make in any given case 

 of bacterial poisoning. 



The results of such observations are of the greatest 

 practical importance. It was found, for example, 

 that after a patient is inoculated with a certain quan- 

 tity of devitalized disease germs, his "opsonic" index 

 for a time falls; showing that the tissues are not able 

 immediately to neutralize fully the weakening effect 

 of the poison. Wright terms this period the "nega- 

 tive phase." 



But presently, in case the inoculation has been 

 properly apportioned in quantity, the index rises, 

 in token that the blood is being surcharged with 

 antitoxines. This so-called "positive phase" pres- 

 ently reaches a maximum and then begins to recede. 

 Repeated inoculations, however, carry it to a relative- 

 ly high level, in token that the blood is for the time 

 being highly charged with protective anti-bodies and 

 opsonins. This is the condition of immunity. It is 

 the condition of a patient for a time after his recovery 

 from an acute infectious disease. 



But if the repeated inoculations had been made 

 during the "negative phase," the system would have 

 staggered, as it were, under the increasing burden, 

 and injury instead of good would have resulted. 

 This it appears had often been the case in the use 

 of Professor Koch's widely heralded "tuberculin," a 

 bacterial vaccine, before the opsonin test was known. 

 Among the first practical results of the new method 



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