446 PATHOGENIC MICROORGANISMS 



happen, however, that occasional strains will react irregularly on 

 different preparations of inulin. These irregularities must be taken 

 into consideration when this test is used for differential purposes. 



Isolation. For the isolation of pneumococci from mixed cultures 

 or from material containing other species, such as sputum, surface 

 smears of the material are made upon plates of neutral glucose-agar, 

 glucose-serum-agar, or blood agar. According to the number of 

 bacteria present in the infected material, it may be smeared directly 

 upon the plate, or diluted with sterile broth before planting. After 

 incubation for twenty-four hours, the pneumococcus colonies are 

 easily differentiated from all but those of streptococcus. With 

 practice, however, they may be distinguished from these also, by 

 their smoother edges and greater transparency and flatness. 



The easiest way to isolate pneumococci from mixed culture and 

 especially from material from patients like sputum, pulmonary 

 exudate, etc., is injection ^nto white mice. When sputum is used 

 the sputum should be washed by gently rinsing in successive watch 

 glasses or pipette plates containing salt solution or broth. It can 

 be injected directly into a white mouse, intraperitoneally, or, if very 

 stringy or dry, can be rubbed in a mortar with a little broth before 

 injection. Great care must be taken not to inject too much material. 

 The details of this method are given in connection with clinical 

 considerations in a subsequent paragraph. If virulent pneumococci 

 are present, death will occur within 24 hours, or thereabouts. Pneu- 

 mococci will be found in pure culture in the heart's blood and in 

 large numbers in the peritoneal exudate. 



PNEUMOCOCCUS TYPES. As stated above, Neufeld and Haendel 29 

 in 1910 found that pneumococci were by no means all alike, sero- 

 logically. Although all the true pneumococci have morphological 

 and cultural characteristics which would appear to classify them as 

 a single species, it was found that within this apparently homologous 

 group there were sharp serological differentiations. Dochez and 

 Gillespie 30 not only confirmed the work of Neufeld and Haendal, but 

 made a careful study of pneumococcus types as they occurred in 

 America, both by agglutination reactions and by protection tests on 

 mice. They isolated a large number of pneumococcus strains, and 

 immunized animals with them. The sera of these animals woro now 



29 Neufeld and Ha,endel, Arb. a. <1. k. Gsndhtsamte, 34, 1910, 293. 

 and Gillespie, Jour, of the A. M. A., 61, 1913, 727. 



