MORPHOLOGY 647 



Lehmann it is not uncommon to find gram-positive individuals in preparations of 

 the Meningococcus. 



2. Cultural characteristics. 



Conditions of growth. The Meningococcus is a strict ae'robe. Growth 

 will only take place at temperatures between 25 C. and 42 C., the optimum 

 temperature being 37 C. In attempting to isolate the organism it maybe 

 difficult at first to obtain cultures, but once established growth takes place 

 quite well on the ordinary media. Media which contain blood or serum 

 (such as human-blood-agar, ascitic-agar and liquid rabbit serum) are particu- 

 larly useful, and should be employed for the primary cultures. 



Characters of growth. Agar. When large quantities of pus rich in meningo- 

 cocci are sown on agar a small number of colonies appear. In 24 hours these 

 attain a diameter of 2 mm., are raised with the surface flattened and borders 

 rounded greyish, and at first transparent subsequently becoming opaque 

 in the centre. 



Blood-agar. Ascitic-agar. Early sub-cultures give isolated colonies having 

 the same characteristics as those on agar, but after several sub-cultures the 

 colonies become confluent and form a copious greyish deposit with wavy 

 edges. 



Kutscher recommends agar made with placenta. Macerate a chopped-up placenta 

 in twice its weight of water, and to each 100 parts of maceration add 2*5 

 parts agar, 0'5 parts salt, 1 part glucose, 2 parts peptone (Chapoteaut). Prepare 

 as for ordinary agar, make slightly alkaline and to 3 parts of the product mix 1 part 

 of ox serum previously heated to 60 C. 



Broth. In early sub-cultures either no growth occurs, or it may be a very 

 minimal amount insufficient to render the medium cloudy, a few coherent 

 masses and a little deposit being found. When acclimatized the cultures may 

 become more abundant and assume the same characteristics as in serum 

 broth. 



Serum-broth. Ascitic-broth. Coherent masses are first seen and then 

 towards the third day a greyish, thin, delicate film appears. 



Rabbit serum. A slight cloudiness with formation of coherent masses. 



Milk is not coagulated by the growth of the organism. 



Potato. Very fine, greyish deposit. 



SECTION III. BIOLOGICAL PROPERTIES. 

 1. Biochemical reactions. 



The Meningococcus ferments glucose and maltose, but has no action on 

 laevulose. saccharose and inulin. 



Media containing glucose and maltose. If to media containing glucose or 

 maltose litmus solution or neutral red be added to serve as indicators, such 

 media can be used for the diagnosis of the Meningococcus. 



The Meningococcus forms acid out of glucose and maltose and turns the 

 litmus red. To tubes of lactose agar add one-third its volume of ascitic fluid 

 (p. 53) and about 1 c.c. of litmus solution and set in the sloped position. 



Buchanan recommends Loeffler's serum-broth containing 1 per cent, glucose 

 and 0*01 per cent, of a 1 per cent, solution of neutral red. This medium at 

 first of a yellowish colour is turned pink in about 24 hours by the Meningo- 

 coccus. Sloped tubes of lactose-ascitic-agar containing a trace of neutral red 

 may also be used. 



The meningococcus produces no indol. 



