PATHOGENIC BACTERIA. 303 



Extensive studies of the pneumococcus were made under the auspices of the 

 Medical Commission for the Investigation of Acute Respiratory Diseases of 

 the Department of Health of the City of New York.* These studies covered 

 the matter of the occurrence of the organisms in the throats of healthy in- 

 dividuals, from persons suffering from various diseases; the various cultural 

 pecuharities, the comparison between the pneumococcus and streptococci, the 

 agglutination reaction, staining peculiarities, and pathogenic properties. 



SchottmuUert and Rosenowf independently of one another 

 found that the pneumococcus presented very characteristic ap- 

 pearance when grown on agar to which rabbit or human blood 

 is added. The medium recommended by Rosenow is pre- 

 pared by adding 0.3 to 0.5 c.c. of sterile defibrinated blood to 

 the tube of melted agar cooled to 45° C. Upon this medium 

 the colonies grow larger than on other media, and they have a 

 distinct green color, and are, furthermore, surrounded by a nar- 

 row zone in which the blood-corpuscles are destroyed. This 

 zone is always opaque and has a greenish tinge. The pneumo- 

 coccus remains viable and retains its virulence for a remarkably 

 long time when it is cultivated upon this medium. RuedigerJ 

 has shown that the green color of the colonies of pneumococcus 

 in this medium is due to the production of an acid, probably 

 lactic. 



Buerger and Ryttenberg§ have come to the following con- 

 clusions: The fermentation of inulin is of limited value for the 

 differential diagnosis between pneumococci and streptococci. 

 Pneumococci may lose the power to produce acid in this 

 carbohydrate either temporarily or permanently. Both pneu- 

 mococci and streptococci may produce precipitation in glucose- 

 serum-agar. Both may cause hemolysis in blood-agar. The 

 diagnosis may be made when everything else fails by use of 

 the capsule staining and animal inoculation. An organism 



*Park and Williams; Collins; Longcope and Fox; Norris and Pappenheimer; 

 Duval and Lewis; Buerger; Hiss and others; Wood; Longcope. Journ. Ex- 

 per. Med. Vol. VII., 1905, pp. 401-626. 



fRosenow. Journ. Infectious Diseases. Vol. I., 1904, pp. 2S0-312. 



XJourn. Infect. Diseases.. Vol. III., 1907. pp. 663-665. 



^ Journ. Infect. Diseases. Vol. IV., 1907. pp. 609-616. 



