THE FRIEDLANDER GROUP 669 



substance, which stains less intensely than the bacilli. There are, moreover, non- 

 capsulated variants, which morphologically and culturally resemble the coliform 

 bacilli ; these often become predominant in old cultures. The organisms are noD- 

 motile and non-sporing. They stain easily, sometimes show bipolar staining, and 

 are Gram-negative. 



The capsule of these organisms is formed not only in the animal body but in 

 culture. To demonstrate it in body fluids, it is sufficient to fix it by heat, and 

 stain with carbol-fuchsin or methylene blue. To demonstrate it in culture, it is 

 advisable to suspend the bacilli in a low dilution — not higher than 1/5 — of serum, 

 dry in air, and fix in a saturated solution of corrosive sublimate before staining 

 (Toenniessen 1912). 



Chemical examination of the capsule has revealed the presence of a nitrogen- 

 free carbohydrate material, which according to Toenniessen (1921) and Kramar 

 (1921) is a polysaccharide of galactose ; but Heidelberger, Goebel and Avery 

 (1925) regard it as a polysaccharide containing glucose. The capsule appears to 

 consist of gum. This substance may be separated from the bacilli in the following 

 manner (Toenniessen 1921) : The organisms are dried, suspended in water, to 

 which 1 per cent. KOH is added, and heated until the gum covering passes into 

 solution. On cooling, the undissolved bacilli form a sediment, and the opalescent 

 supernatant fluid is pipetted ofi. This is acidified with acetic acid, and 

 3 volumes of 91 per cent, alcohol are added, when a heavy precipitate of the 

 gummy substance occurs ; this precipitate is purified by dissolving it in distilled 

 water, and re-precipitating it with acid and alcohol. In the pure state it is a loose, 

 snow-white powder, giving an opalescent solution in distilled water, acids, or 

 alkalies ; it is free from nitrogen, and does not reduce Fehling's solution. It has 

 special antigenic properties, which will be referred to later. 



Cultural Reactions. — One of the characteristic features of this group is the 

 luxuriant, greyish-white, mucoid, almost diffluent, growth on agar. This results 

 no doubt from the presence of the gummy envelope around the bacilli, containing 

 a high proportion of water — 92 per cent. (Toenniessen 1921). The condensation 

 water on an agar slope is converted into a greyish-white mucoid mass. In broth 

 the organisms grow freely, giving rise after a few days to a marked viscosity, so 

 that the medium takes on the consistency of melted gelatin. Great stress used 

 to be laid on the nail-headed growth in stab gelatin cultures ; a circular, convex 

 growth may occur on the surface, with a filiform growth in the stab, the whole 

 resembling a round-headed nail. This appearance is not constant, and is given 

 only by some strains ; it depends too on the amount of gelatin in the culture ; 

 with small amounts, about 4 per cent., the surface growth is flat (Friedlander 1883). 

 There is no liquefaction of the gelatin, but often a large napiform bubble of gas 

 accumulates just beneath the surface, giving on first sight the appearance of lique- 

 faction. On potato there is a moderate creamy-yellow mucoid growth, later 

 turning to a buff or light cafe-au-lait colour. 



The cultural appearances of the Friedlander group are subject to considerable 

 variation. This is due to the production of variants which have different forms of 

 growth from the parent strain. Toenniessen (1913) found that when the usual 

 mucoid type was kept in the incubator and subcultured every few days, non- 

 mucoid variants rapidly appeared. As the original colonies grew older, white, 

 more or less translucent peripheral sectors developed, which on microscopical 

 examination were found to consist largely of non-capsulated bacilli ; these could 



