532 NEISSERIA 



appear frequently in the form of dense clumps with occasional isolated organisms. 

 One difierence in arrangement that serves to distinguish Gram-negative from 

 Gram-positive diplococci is the way in which the main axis of the oval is directed ; 

 with the Gram-negative cocci this axis is always at right angles to the axis joining 

 the two cocci ; with the Gram-positive cocci it is often coincident with it. In 

 other words, pairs of Gram-negative cocci are usually compressed laterally, 

 Gram-positive cocci often longitudinally. As a rule the Gram-negative cocci are 

 decolorized without difficulty, but some members tend to retain the gentian violet, 

 and so take on an indeterminate colour, which is most confusing. The most 

 notable example of this is Jaeger's coccus or the Diplococcus crassus ; in a 

 single film Gram-positive and Gram-negative, and numerous other cocci with an 

 indeterminate colour, are found lying side by side. One reason for the indeter- 

 minate staining of some of the Gram-negative cocci is the tendency they have to 



be arranged in groups or dense 



, . '' clumps ; once these have been 



"*. • . * *• stained with gentian violet, they 



•"■ ' * are not easily decolorized. Hence 



■ •" • ... 



/ ^ ~ * I * • it is important always to make 



^ • . . .* ■/ # * films as thin and as uniform as 



^ . ^ *. .« *>^ * ' „ possible. In young cultures the 



*^ : '*•, i '" ' *\ cocci stain fairly evenly, but after 



.* ; , * • » *^ • * • » about 24 hours autolytic changes 



• I '''... set in, with the result that so- 



• • • • " 



' f ^ » • ' ' called involution forms appear ; 



.••.*«• ,' *-• these are generally large, swollen 



•• *.*.*,*"*,* , '^ * . cocci, which stain poorly. Both 



» "^ i the meningococcus and the gono- 



t- , .J * . , . , coccus are characterized, as com- 



• ■ ••• • pared with most other neisserise, 



: • _ ♦ • by the frequency with which such 



Fig. l06.-^Neisseria meningitidis. f^^^^ appear ; and it may be 



From a serum agar slope culture, 4 days, 37° C. ^O^^d that many of the large 



( X 1000). swollen forms, in cultures of these 



species, stain deeply and uni- 

 formly. J. E. Gordon (1921) described a variety of N. catarrhalis in which the 

 degenerative forms began to appear after the 4th hour, but this is unusually early. 

 Some workers have described the presence of Babes-Ernst bodies or metachro- 

 matic granules in members of this group. Elser and Huntoon (1909) state 

 that the meningococcus, when stained with Loeffler's methylene blue, often 

 shows a brightly stained central spot, whilst the remainder of the cell is scarcely 

 coloured ; with Neisser's stain the granules stain bluish-black, the cell body 

 brown. Marx and Woithe (1900) found these granules in gonococci, but only 

 in organisms taken from the florid stage of gonorrhoea ; they state that the 

 whole cell may appear filled with granules. Capsules are demonstrable in some 

 freshly isolated strains of meningococci (Clapp et al. 1935), and in the organism 

 known as Diplococcus mucosus. 



Growth Requirements. — Culturally many of the Gram-negative cocci are charac- 

 terized by a reluctance to grow on ordinary media, especially fluid media. Most 

 of the nasopharyngeal cocci will grow— though often poorly — on nutrient agar, 



