OCCUKRENCE OF PNEUMOCOCCUS 231 



culture. Two per cent sodium taurocholate may be similarly 

 used. 



The facts that in cultures the pneumococcus often grows in 

 chains, and that occasionally streptococci are found to develop 

 capsules, have raised the question of the relationship of the 

 pneumococcus to other streptococci. In determining the true 

 pneumococci, biological as well as morphological characters must 

 be studied, and here the bile solubility of the pneumococcus, 

 its failure to produce hemolysis, and its capacity of ferment- 

 ing inulin are the important characters. It must be stated, 

 however, as bearing on the close relationships of the pneumo- 

 cocci and streptococci, that Rosenau believes he has succeeded 

 in transforming streptococci into capsulated organisms having 

 all these biological features of the pneumococcus. 



Considerable attention has been directed to a group of cocci 

 originally described by Schottmuller, isolated from various dis- 

 ease conditions in man (pneumonia, meningitis, suppurations), 

 which besides possessing voluminous capsules have these sur- 

 rounded by a viscous material which gives a slimy consistence 

 to cultures' and also to pathological exudates. These are related 

 to the pneumococci on the one hand and to the streptococci on 

 the other. The work of the Rockefeller investigators (v. infra) 

 suggests that these organisms ought to be classified into two 

 groups. (1) The pneumococcus mucosus. This organism tends 

 to be not so pointed as the ordinary pneumococcus, and its 

 colonies are larger ; it is non-hsemolytic on blood agar, soluble 

 in bile, gives rise to acid and clot in Hiss's inulin serum-water, 

 and is very pathogenic to white mice and rabbits. Anti-sera 

 produced by strains of this coccus, while showing cross agglutina- 

 tion towards members of their own group, do not agglutinate 

 streptococci and usually also not other pneumococci. (2) The 

 streptococcus mucosus. This organism is generally round, occurs 

 in chains, and the colonies are less transparent than those of the 

 pneumococcus ; it is usually non-hsemolytic, is not soluble in 

 bile, does not ferment inulin, and is less pathogenic to mice than 

 the last. Thus while the pneumococcus mucosus is practically a 

 true pneumococcus, the streptococcus mucosus forms a connect- 

 ing link with the true streptococci. 



The Occurrence of the Pneumococcus in Pneumonia and 

 other Conditions. — The pneumococcus occurs in every variety 

 of the disease — in acute croupous pneumonia, in broncho- 

 pneumonia, in septic pneumonia. In a case of croupous pneu- 

 monia the pneumococci are found all through the affected area 

 in the lung, especially in the exudation in the air-cells. They 



