70 C. G. A. ROOS 



The meningococcus is an aerobic organism but like many 

 other aerobes when first grown aerobically and then transferred 

 to an atmosphere of hydrogen, it can be kept ahve longer than 

 when oxygen is present. Cultures of meningococci were grown 

 aerobically for twenty-four hours at 37.5°C. and then trans- 

 ferred to a Novy jar, the air of which was replaced with hydrogen 

 by means of a Kipp apparatus and a Schutte vacuum pump; 

 the jar contained pjrrogaUic acid and sodium hydroxide which 

 were permitted to mix after the air had been replaced several 

 times by hydrogen. These cultures were then kept in the incu- 

 bator; after ten weeks good growths were obtained on the first 

 transplant. 



The appearance of the meningococcus growth on potato 

 blood agar is not very characteristic. After twenty-four hours 

 growth at 37.5°C. the individual colony has reached the size 

 of a small pinhead. It is gray in color, smooth and rather moist 

 looking, of an amorphous consistency, the surface elevation varj'^- 

 ing from convex to pulvinate with border entire. With age, the 

 color of the colony changes to dull gray, the consistency becomes 

 tenacious, and the surface elevation more of the raised type. 



Although the production of pigment by some organisms is 

 facilitated on potato blood agar, the area of discoloration char- 

 acteristic of numerous strains of streptococci, — notably the 

 Streptococcus viridans and pneumococcus on blood agar, and 

 some Gram negative cocci on glucose agar as described by 

 Elser and Huntoon — has never been observed by us with any 

 strain. 



All of our thirty-eight strains have invariably remained Gram 

 negative, regardless of culture medium used or age of culture. 

 Occasionally, more frequently in old cultures, a few organisms 

 may be seen that do resist for a .time the action of the decoloriz- 

 ing agent and thus appear to be Gram positive. However, this 

 is usually an indication of faulty technique or of contamination. 



Arrangement in pairs is most conmion, although single cocci 

 and groupings in tetrads are numerous, with certain strains 

 especially. True chain formation has never been observed. 

 '\'ariations in the size of organisms in the different strains are 



