21 



held in London on December 12-14, 1921. " It is very desirable," 

 to quote from the memorandum submitted to the Conference by 

 Dr. Madsen, " to obtain information regarding the occurrence 

 11 of different types in different countries in order that the thera- 

 " peutic effect of pneumococcus serum may be properly deter- 

 " mined. It is proposed, therefore, to start such an investigation 

 " by inviting as many institutions as possible to examine strains 

 " of pneumococci derived from pathogenic cases according to a 

 " uniform plan." 



In a preliminary *note on the serological types of pneumo- 

 cocci occurring in 100 consecutive cases of lobar pneumonia, 

 derived mainly from the London area, I showed that the 

 American Types I, II and III were demonstrable in approxi- 

 mately the same proportions as were found in the United States 

 by the workers of the Rockefeller Institute. The report which I 

 have now prepared for the Ministry of Health deals with a more 

 extended inquiry into the incidence of the various types of 

 pneumococci, together with my observations on the technique 

 in the diagnosis of type and on the question of the immunological 

 independence of types. Standard type strains and sera, received 

 direct from the Rockefeller Institute, formed the starting point 

 of this work on pneumococci. 



I am much indebted to Dr. R. C. Harkness, Dr. C. Spurrell 

 and many other medical officers of institutions for material used 

 in this investigation. 



Technique for the Differentiation of Type. 



Isolation of Pneumococci. 



The material received from the majority of the cases was 

 sputum ; in a small proportion pieces of consolidated lung tissue 

 were examined. About 0*5 c.c. of sputum (or lung emulsion) 

 was injected intraperitoneally into a mouse and the pneumococcus 

 was grown from the heart's blood. The first culture was made 

 direct from the blood into blood broth medium consisting of a 

 mixture of equal parts of denbrinated rabbit blood and trypsin 

 broth. At the same time a blood agar plate was sown from which 

 colonies were selected if, as occasionally happened, the first 

 culture was contaminated with other infective organisms from 

 the mouse's blood; the influenza bacillus frequently multiplied 

 in the blood of the first mouse but died out in subsequent passages 

 through the mouse. An attempt was always made to avoid 

 growing the strain on solid media in order not to weaken the 

 virulence. Latterly, however, a number of single colony cultures 

 have been tested from each strain, as it was found that the heart's 

 blood of the mouse sometimes contained more than one type 

 of pneumococcus. Occasionally, also, cultures were grown direct 

 from the sputum as well as through the mouse; in the former 

 case colonies were picked from blood agar plates. The spleen 



* Lancet, July 30th, 1921, p. 226. 



