294 THE MENINGOCOCCUS GONOCOCCUS GROUP 



the sediment distributed as densely as possible in the manner indi- 

 cated. A few small, transparent, round colonies are usually obtained 

 when relatively large amounts of material are inoculated. The first 

 growth upon artificial media is difficult to obtain; secondary trans- 

 fers, if made within three days from initial cultivations, are usually 

 successful and development is somewhat more vigorous. It should 

 be emphasized that relatively large amounts of cocci must be inocu- 

 lated to insure growth in artificial media. 1 Little or no growth occurs 

 in plain broth; the addition of calcium carbonate 2 to dextrose broth 

 makes a favorable medium for the development of the organism. 

 Ascitic and serum broths are suitable media for the meningococcus. 

 A coherent sediment gradually accumulates in these media and a 

 delicate pellicle usually forms on the surface after a few days. Secon- 

 dary transfers in milk usually grow, but there is little or no detectable 

 change in the physical properties of the medium. 



The meningococcus is essentially an aerobic organism, at least in 

 its development outside the human body. The optimum tempera- 

 ture of growth is 37 C., and growth ceases when the temperature 

 exceeds 42 C. or falls below 25 C. The organism is soon killed by 

 low temperatures. Stock cultures can not be maintained at the 

 temperature of the ice-box; they should be kept at temperatures 

 between 32 and 38 C. Frequent transfers (every two or three days) 

 must be made to maintain the viability of the organism ; exceptionally 

 strains are met with which become acclimatized to the conditions 

 obtaining in artificial media to such a degree that transfers made at 

 less frequent intervals suffice to maintain the viability of the culture. 



The meningococcus exhibits little resistance to heat, drying or the 

 action of chemical agents. Five minutes' exposure to 65 C. or two 

 minutes' exposure at 80 C. suffices to sterilize the culture. Drying 

 for a few hours at 20 C. is likewise fatal to the organism. Exposure 

 of the organism to carbolic acid broth (1 to 800) inhibits development, 

 and drying in the dark for seventy-two hours is fatal; sixty hours' 

 exposure to drying is insufficient to kill the organisms. 3 



Products of Growth. Meningococci are culturally very inert. No 

 proteolytic enzymes have been demonstrated; gelatin and blood 

 serum are not liquefied, and no coagulation or peptonization of milk 

 occurs. Indol, skatol, phenol or other products of similar nature are 



1 The organisms, like gonococci, degenerate rapidly in artificial media. This may 

 explain the necessity of transferring the organisms at frequent intervals. 



2 Bolduan, New York Med. Jour., 1905, May 13. 



3 Councilman, Mallory and Wright, loc. cit., p. 78. 



