132 BIOLOGY OF PNEUMOCOCCUS 



which appears a halo of light. When the serum and organisms are 

 of different types, the pneumococci are of their usual size and are 

 barely visible. This Quellung or swelling phenomenon is a distinct 

 and specific reaction between the capsular substance of the pneu- 

 mococcal cell and antibody of the same type. In the same year as 

 that of Neufeld and Etinger-Tulczynska's publication, Sabin 1207 

 applied the method in the examination of sputum of one hundred 

 cases of lobar pneumonia. The results with Type I and II organ- 

 isms were found to correspond exactly to those of the mouse test. 

 In two cases Sabin was able to identify Type I organism, whereas 

 the results by older methods were negative. Furthermore the test 

 was sometimes positive in purely salivary specimens. 



In the next year (1934), after an experience of sixteen months, 

 including two months in which they extended the use of the Neu- 

 feld test to all types including those from IV through XXXII, 

 Beckler and MacLeod 96 confirmed the results by other methods in 

 96 per cent of the examinations. They unqualifiedly recommended 

 this method because of its accuracy, simplicity, rapidity, and the 

 small amount of sputum required. 



Summary 



The species Diplococcus pneumoniae has been divided by means 

 of agglutination and other immunological methods into thirty-two 

 separate and distinct serological types. There is evidence at hand 

 that points to the existence of pneumococci that may belong to 

 types other than those already established. Further investigation 

 may reveal some new type identities, but the present list comprises 

 the great majority of the members of this bacterial species. On the 

 basis of cross reactions, there appears to be some relation between 

 organisms of Types II and V, III and VIII, VII and XVIII, and 

 XV and XXX, but the resemblances are not sufficiently close to 

 invalidate the current classification. In nature there appears to be 

 a stability of the types, although, as will be shown in the succeed- 



