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ways inject the animal with the same quantity of material and 

 read of the result after a certain time, fixed in advance. 



If the virulence-estimation has a positive result we will 

 probably not be far from the truth if we infer that the microorga- 

 nism is a diphtheria bacillus, wich may produce a toxin also 

 harmful to man. The same cannot be said of a negative result. 



As we have selected one or a few bacilli among millions 

 and millions from one part of the mucous membrane of the 

 throat, as we have cultivated it after à fixed schema and inocu- 

 lated it on a guinea-pig, and as we now find that after a 

 certain time the animal shows no signs of disease, we conclude, 

 that in the throat of the person examined no diphtheria bacilli 

 are to be found, which may produce by growth on a human 

 mucous membrane a toxin, which may be harmful to man. 



This conclusion rests after all on too weak a basis even for 

 praxis. What if we had altered the scheme a little? It we had 

 swabbed another part of the throat, or selected another bacte- 

 rium for further cultivation or if we had given it another 

 medium for the toxinproduction and prolonged the time of the 

 growth a little or injected a larger quantity and observed the 

 guinea-pig a little longer? Might not the result have been 

 different? And above all we have to bear in mind, that a 

 guinea-pig cannot be compared in every way to man. .\ bacillus, 

 which may be quite harmless to a cavia, may surely be patho- 

 genic to man ; the following experience may illustrate this. 



In October 1914 a few soldiers in the south of our country 

 got angina with membrane-formation and a few days slight 

 raise of temperature. The medical man thought it diphtheria 

 and material was sent to us. We found bacteria in it, which 

 were positively diagnosed by us as real diphtheria bacilli. 



A small epidemic of angina arose among these soldiers ; 

 persons in the same lodgings, or who came in some other way 

 in closer contact, infected each other and in all 15 had to be 

 taken to the infirmary with throataffections. Some of them 

 were scarcely ill, others had distinct membranes in their throat 

 and with the great majority diphtheria bacilli could be diagnosed. 

 Of a great many we isolated a pure culture and it was tried 

 in every way to get a toxin harmful to guinea-pigs. We were 

 not successful however, neither by subcutaneous nor by 



