PATHOGENICITY FOR MAN 231 



for a year on over one hundred subjects, found that while the type 

 of Pneumococcus usually proved to be the same in successive tests 

 on a given individual, in many cases there were rapid and frequent 

 changes in the types present. The relative infrequency of organ- 

 isms of the first three types, so often observed in the mouth flora of 

 healthy persons, is also to be noted in Gundel's report. Type I 

 pneumococci occurred in 0.8 per cent, Type II in 0.4 per cent, 

 Type III in 6.7 per cent, and organisms of Group IV (Gundel's X) 

 were present in 60 per cent of the individuals tested successively 

 throughout the year. 



In a continuation of the study, Gundel and Okura, 573 with even 

 more painstaking methods, investigated the occurrence of pneu- 

 mococci of more than one serological type in the same subject. 

 Thirty-eight per cent of the individuals of the series tested car- 

 ried organisms of two or more types, and the frequency of occur- 

 rence was much greater among boys than among girls. The ap- 

 pearance of new types was attributed by the authors to infection 

 from without or possibly to the development of a type which had 

 been suppressed by the dominance of the first type found. Gundel 

 and Okura did not agree with Neufeld and Etinger-Tulczinska 984 

 that infection of the nasal or buccal mucous membrane may lead to 

 specific immunity against the infecting type without eliciting any 

 apparent or at least definite morbid symptoms, since repeated 

 serological tests failed to reveal any specific antibodies for the 

 types carried for protracted periods. The explanation that the 

 non-invasiveness of pneumococci existing in the normal mouth 

 could be due to the fact that the organisms there undergo dissocia- 

 tion into rough and, therefore, avirulent forms was opposed by 

 Gundel and Schwarz, 575 who encountered no such variants in their 

 investigations. This opinion was further supported by the results 

 of a slightly earlier series of virulence tests on pneumococci iso- 

 lated from normal and pneumonic sputums, which would seem to 

 show that virulent strains exhibit few if any signs of variation in 

 vivo. Gundel and Wasu 578 concluded that the vegetative pneumo- 



