87 



in the present case because each man was questioned about 

 his place of residence for the last 3 months, and these places 

 have always been distributed indiscriminately over the whole 

 country. 



In the graphic representation the number of influenza cases 

 reported each month for the whole country are plotted as a 

 staircase curve and also noted along the upper margin of the 

 figure. The other curve in the diagram gives the percentage 

 of positive findings of Pfeiffer's bacillus. The magnitude of 

 the mean error is also indicated by the double arrows. 



What this mean error expresses is that uncertainty of 

 the percentage values, which is a result of the limited ex- 

 tent of the material. It will be seen that the mean error is 

 so small compared with the large variations in the occur- 

 rence of Pfeiffer's bacillus that we cannot assume a very dif- 

 ferent result would have been obtained even if the investiga- 

 tions had encompassed similar material of 10 or 100 times 

 the dimensions. 



The excellent agreement between the distribution of influenza 

 and Pfeiffer's bacillus among the population, as depicted by 

 the curve, hardly needs any further comment. Naturally we 

 cannot decide whether this agreement is direct or indirect. 

 Future investigations will show the manner of distribution of 

 Pfeiffer's bacillus at different seasons of the year apart from 

 influenza periods. That the potent factor is not the time of 

 the year alone, seems however probable from 1 a comparison 

 between the 4 investigations in September 1918, 1919, 1920, 

 and 1921. 



We have now seen that the shape of the curve cannot 

 be explained as due to a fortuitous error in consequence of 

 the restricted scope of the material. This does not however 

 exclude that it might be caused by variations in the constitution 

 of the nutritive medium 1 or other irregularities of the tech- 

 nique. This explanation must however also be rejected, be- 

 cause it would be a most improbable occurrence that a curve 

 should be formed in this manner, the form of which corre- 

 sponded so well to the influenza epidemics. It is instructive 

 to compare the last of the above investigations (24. IX. 21) 

 which gave 10o/ of Pfeiffer's bacilli, with the last of those re- 

 ported below from the Jsegersborg camp (17. IX. 21). In the 



