450 PATHOGENIC MICROORGANISMS 



concludes that most strains form gas from dextrose and levulose, but 

 that lactose is fermented by some only. About two-thirds of the gas 

 formed is hydrogen, the rest CO2. Acid formation, according to Strong, 

 is also subject to much variation among different races. Similar studies 

 by Perkins * show that most of the ordinary cultural characteristics of 

 bacilli of this group are extremely variable and can not serve as a basis 

 for differentiation. Reactions on sugars, however, are more constant. 

 Perkins suggests the following tentative division classes on this basis: 



I. All carbohydrates fermented with the formation of gas. 



II. All carbohydrates, except lactose, fermented with the formation 

 of gas. 



III. All carbohydrates, except saccharose, fermented with the 

 formation of gas. 



Type I. corresponds to B. aerogenes (Migula), Type II. to B. 

 Friedlander or Bacteriimi pneumoniae (Migula), and Type III. to 

 Bacillus lactis aerogenes. 



Differentiation by means of serum reactions has not proved satis- 

 factory. ^ 



Pathogenicity. — ^When Friedlander first described this microorganism, 

 he assumed it to be the incitant of lobar pneiunonia. Subsequent re- 

 searches by Weichselbaum ^ and others have shown it to be etiologically 

 associated with pneumonia in about seven or eight per cent of all cases. 

 The percentage in this country is probably lower. Such cases can often 

 be diagnosed by the presence of the bacilli in the sputum, which is pecul- 

 iarly sticky and stringy. Cases of Friedlander pneumonia are extremely 

 severe and usually fatal. The bacillus has been found in cases of ulcer- 

 ative stomatitis and nasal catarrh; in two cases of severe tonsillitis in 

 children (Zinsser) ; in the pus from suppurations in the antrum of High- 

 more and the nasal sinuses (Frankel and others), and in cases of fetid 

 coryza (ozena), of which disease it is supposed by Abel " and others to 

 be the specific cause. Whether the ozena bacillus represents a separate 



' Perkins, Jour, of Infect. Dis., I, No. 2, 1904. 



2 J. G. Fitzgerald, who has recently made a careful study of the mucosus cap- 

 sulatus group has concluded that present methods do not permit a subdivision of 

 these organisms into separate species. He offers the following "tentative suggestion": 

 It is conceivable that mutations based on the necessity of maintaining a parasitic 

 existence have caused Gram-negative bacilli found normally in the body elsewhere 

 than in the intestinal tract to develop capsules for protection and a new group has 

 arisen which we designate B. mucosus capsulatus; and the varieties B. aerogenes 

 and B. acidi lactici connect the group with the non-encapsulated colon group." 



^ Weichselbaum, loc. cit. * Abel, Zeit. f . Hyg., xxi. 



