234 BIOLOGY OF PNEUMOCOCCUS 



persons studied. Of the 500 strains isolated, 97 per cent proved to 

 be serologically specific. The organisms formed smooth colonies 

 and were for the most part avirulent for mice. Pneumococci of 

 Types I and II were obtained from one and two individuals respec- 

 tively on one occasion only. Type III organisms were encountered 

 in nine subjects, Type VIII in nine, Types XVI and XVIII in 

 three persons for varying periods in each case; and avirulent, 

 atypical strains were isolated from thirteen persons on single and 

 scattered occasions. The presence of the last-named organisms was 

 considered by the authors as having no association with any type- 

 transformation in vivo. 



The strains isolated in successive cultures from a given carrier 

 were, with rare exceptions, of the same serological type and similar 

 in colony morphology, virulence for mice, and other biological 

 characters. The persons observed differed consistently with respect 

 to the occurrence of pneumococci. Some were Pneumococcus-free, 

 some were transient carriers, some periodic, and some chronic car- 

 riers, and evidence was presented in the communication that these 

 differences were due to variations in host-resistance. The incidence 

 of pneumococci in all the individuals included in the study under- 

 went seasonal fluctuations corresponding to changes in the preva- 

 lence of coryza and sore throats in the same persons, an observa- 

 tion reported by Longcope and Fox 825 in 1905. 



Further data on the variety of pneumococci to be found in the 

 nose and throat flora of individuals selected only for the non- 

 existence of pneumonic disease among them, are furnished by the 

 report of Hoyle (1932) 662 who, like Webster and Hughes, carried 

 out bacteriological observations on normal persons over periods of 

 one, one and a half, and two years. Of the forty subjects, on one 

 occasion — and the only one — Type I Pneumococcus appeared dur- 

 ing an acute attack of coryza, the patient developing lobar pneu- 

 monia three or four days later. Type II organisms were never de- 

 tected. Type III pneumococci were isolated on four occasions, once 

 late in a cold, in one case persisting for fourteen days in the mouth 



