90 ILLINOIS ACADEMY OF SCIENCE 



planted in favorable soil, under favorable conditions it 

 tends for a time to increase in virility. 



(b) After the soil bas been to a degree impoverisbed 

 by any special strain of germ tbe groAvtb will become 

 weaker and more stunted. 



(c) Germs, wlietlier weak or strong, wben transferred 

 to an average soil tend to preserve tbeir former cbar- 

 acter. 



Most elderly persons by virtue of having bad influenza 

 in the epidemic of 1889 or later had therefore a degree of 

 immunity to the germ. Young persons generally had a 

 less degree of uumunity because at the most they had 

 been exposed to an attenuated form of the germ. The 

 normal community is made up of both young and old, 

 and its susceptibility to such a disease may therefore be 

 considered as normal. A community made up chiefly of 

 young people would theoretically have more than the 

 normal degree of susceptibility to the disease, and would 

 prove a favorable soil. We should therefore expect such 

 a coimuunity to show high morbidity and high mortality. 

 This is well represented in Lake County which contained 

 a large Army Camp at Fort Sheridan, and the Great 

 Lakes Naval Training Station. Champaign County con- 

 tains a large universitj^ and the aviation field at Eantoul. 

 There was a camp in Peoria County. On the other hand, 

 communities which had lost an appreciable proportion 

 of their young people, especially if they contained no 

 important business interests which would attract large 

 numbers of people, might reasonably be expected to show 

 a lessened susceptibility. Though the disease might find 

 many victims in such communities we should not expect 

 a high death rate. In the main our study of the records 

 for the State bears out these general conclusions, but we 

 are struck with a marked exception. Winnebago County, 

 containing the largest camp in the State at Rockford is 

 classed as low in morbidity and average in mortality. 

 When, however, we include the figures for the pneumonias 

 we find that its morbidity total Avas very heavy. In most 

 counties the deaths from pneumonia were recorded as less 

 than those from influenza. In Winnebago the deaths 



