120 BIOLOGY OF PNEUMOCOCCUS 



importance, it is the use of the immunologically appropriate se- 

 rum and the promptness of treatment which in many cases may de- 

 termine the issue for the patient. The major effort, therefore, be- 

 sides increasing the accuracy of these tests, has been expended in 

 devising ways of shortening the time elapsing between the collec- 

 tion of the specimen and the identification of the serological type 

 of the infecting Pneumococcus. 



MOUSE PROTECTION TEST 



It was Neufeld and Haendel 991 who, in 1910, realizing the im- 

 portance of the delay involved in the isolation, cultivation, and 

 identification of pneumococci from infected material, saw in Unger- 

 mann's 1433 suggestion of testing cultures on the basis of phagocytic 

 action, possibilities for reducing the time factor. Ungermann's 

 plan was to inject a mouse intraperitoneally with sputum, then 

 several hours later to inject immune serum, and after a further in- 

 terval of an hour and a half, to kill the mouse and make stained 

 smears of the exudate from the surface of the liver. When the 

 serum corresponded immunologically with the culture, marked 

 phagocytosis of the cocci took place. 



The use of the mouse as a vital differential medium cut short the 

 time usually required by plating and subculturing and became the 

 foundation of the protection test developed by Cole and his asso- 

 ciates. 86 This method, which is given in detail in the Appendix, im- 

 mediately came into general use, and while in the routine examina- 

 tion of pneumonic material it has given place to the more rapid 

 presumptive tests, it still remains the method of choice for the ulti- 

 mate determination of pneumococcal types. There are certain diffi- 

 culties encountered in the practice of this method, such as the 

 occurrence of pneumococci of more than one type in the specimen, 

 the overgrowth of Pneumococcus by other organisms in the peri- 

 toneal cavity of the mouse, the occurrence of cross-agglutination 

 when undiluted or slightly diluted immune horse serum is used, and 



