478 FU8IF0RMIS 



may grow out into long filaments which are generally curved. Their width is also 

 variable ; not infrequently it is greater near the middle of the bacillus than at the 

 end, giving the organism a fusiform appearance ; the fusiform swellings may be 

 as much as 4-5 fi in diameter. Occasionally the greatest diameter of the bacillus 

 is at one end, so that the organism appears clubbed. Pleomorphism is a marked 

 characteristic of some species. The organisms are arranged singly, in pairs end- 

 to-end, or in chains ; pseudo-filaments, showing evidence of subdivision are common. 

 Some species show false branching, with the result that V- or Y-forms are seen, 

 but true branching does not occur. Some species are said to be motile, but the 

 observations of recent workers render this doubtful. Spores are never formed. 

 The organisms stain with the usual aniline dyes, but staining is often irregular. 

 The reaction to Gram varies with different species. None of the organisms is 

 acid-fast. 



Culturally, growth occurs under anaerobic or microaerophilic conditions and is 

 said to be favoured by the presence of 2 per cent. CO a- Little is known of their 

 respiratory mechanism, but it seems probable that in fluid media they do not 

 produce such low oxidation-reduction potentials as do many of the spore-bearing 

 anaerobes (Dack and Burrows 1935). Some species grow readily in ordinary media, 

 while others require the addition of natural animal protein. According to Slanetz 

 and Rettger (1933), growth is stimulated by aqueous extracts of various vegetables, 

 and a potato extract gelatin medium is recommended for the preservation of stock 

 cultures. The optimum temperature for growth is about 37° C. ; some species 

 will develop at 23°, others not below 30° C. In solid media, colonies frequently 

 do not become visible for 3 or 4 days, and usually remain small. For the isolation 

 of the intestinal non-sporing anaerobic bacteria, Lewis, Bedell and Rettger (1940) 

 recommend a glucose-cysteine agar medium at a pH between 6-3 and 7-0, enriched 

 with yeast-extract and tomato juice, and state that growth is greatly improved 

 by 10 per cent. COo in the anaerobic atmosphere. Little is known of the precise 

 growth requirements of these organisms, though both pantothenic acid and pyruvic 

 acid appear to be essential nutrients for a number of strains (West, Lewis and 

 Militzer 1942). 



The organisms are not particularly resistant ; they are destroyed by exposure 

 to moist heat at 55° C. within an hour. The colonies of some species are highly 

 oxygen-sensitive, dying within an hour of exposure to air (Hine and Berry 1937). 

 The fermentation reactions have been incompletely studied, but some species 

 produce acid and gas in certain carbohydrate media. 



The organisms of this group appear to be obligatory parasites, and may be 

 cultivated from certain inflammatory processes, particularly those accompanied by 

 necrosis and ulceration, as well as from the normal mouth, teeth, and faeces. There 

 seems to be little doubt that some species are primarily responsible for the lesions 

 from which they are isolated ; but the aetiological role of others is probably more 

 of a secondary nature. Many of the species are pathogenic to laboratory animals, 

 producing necrotic lesions and death. Whether a true exotoxin is formed is not 

 yet known. 



Antigenically, little exact information is yet available about these organisms, but 

 there is evidence that differences in antigenic structure do exist between different 

 types. 



The recorded investigations of these organisms are of two kinds : firstly, of 

 organisms found in association with disease processes, and secondly, of organisms 



