Pneumococcus Grouping on a Thousand Cases. 371 



Likewise it very exceptionally produced a similar degree of trans- 

 parency in surrounding medium. Usually the zone about the 

 pneumococcus colony is translucent, hazy, or of ground glass 

 appearance, and frequently with an outer, more or less diffuse 

 methemoglobin ring, varying in color from pale to brownish 

 green. When examined under the low power of the microscope, 

 the zone of clearing rarely was free from "shadow cells," and in 

 those showing haziness, such cells were much more in evidence- 

 If the zone appeared slightly opaque or pigmented, the blood 

 cells showed certain amounts of the changed hemoglobin or met- 

 hemoglobin present. The zone of clearing about the pneumo- 

 coccus colony can hardly be considered a hemolysis in the sense 

 as applied to that produced by the Streptococcus hemolyticus. 

 The first is probably due to an intracellular hematoxin, liberated 

 by autolysis of organisms in the colony, while the second is prob- 

 ably extracellular, elaborated and passed out by the living organ- 

 ism. In the case of the pneumococcus, perhaps it would be more 

 appropriate to designate the change as a pseudo-hemolysis, since 

 it lacks the completeness of action shown by the hemolytic strep- 

 tococcus. Further, the reaction is probably complicated by two 

 independent processes occurring at the same time — methemo- 

 globin formation induced by the living organisms, and a hemoly- 

 sis produced by a hematoxin arising from autolyzed cells, as 

 suggested by Cole's studies on pneumococcus hematoxin, 1 and 

 methemoglobin production by the pneumococcus. 2 



The hemolyzing action of different pneumococcus strains 

 within the same group was found rather irregular; certain ones 

 appeared to possess that ability to a greater degree than others. 

 Even the same strain on repeated tests showed considerable varia- 

 tion. 



The medium reaction (P H 7.0 and P H 8.0) in which the organ- 

 isms were plated produced no apparent variation in growth or 

 hemolytic action at incubator temperature. Also no appreci- 

 able difference in hemolysis could be recognized in a similar series 

 of plate cultures, which were placed in the icebox three days after a 

 primary incubation of 36 hours. Methemoglobin production was 



1 Jour. Exper. Med., 1914, xx, 346. 



2 Jour. Exper. Med., 1914, xx, 363. 



