THE PNEUMOBACILLUS OF FRIEDLANDER 359 



brownish coloration. This latter characteristic distinguishes the growth 

 of this bacillus from that of the bacillus aerogenes, which is otherwise 

 very similar to it morphologically and culturally. On gelatin plates 

 colonies appear at the end of twenty-four hours as small white spheres, 

 which rapidly increase in size. These colonies, when examined by a 

 low-power lens, present a somewhat irregular outline and a slightly 

 granular appearance. The growth on agar is in quite large and moist 

 grayish colonies. On blood scrum abundant, grayish-white, viscid masses 

 arc developed. The growth on potato is luxuriant a thick, yellowish- 

 white, glistening layer rapidly covering the entire surface. Milk is not 

 coagulated. Indol is produced in bouillon or peptone solutions. Milk- 

 sugar and glucose are fermented. Growth occurs at 16 to 20 C., but 

 is more rapid at 37 C. 



Pathogenesis. Friedlander's bacillus is pathogenic for mice and 

 guinea-pigs, less so for dogs, and rabbits are apparently immune. On 

 autopsy after death due to inoculation into the lungs, the pleural cavities 

 are found to contain a seropurulent fluid, the lungs are intensely 

 congested, and in places show 7 limited areas of red hepatization ; the 

 spleen is considerably enlarged, and bacilli are present in the lungs, 

 the pleuritic fluid, and the blood. 



Friedlander's bacillus has been found in man, not only in patients 

 suffering from croupous pneumonia and other respiratory diseases, but 

 also in healthy individuals, and in the outside world. Netter observed 

 it in 4.5 per cent, of the cases examined by him in the saliva of healthy 

 individuals, and Pansini in cases of pulmonary tuberculosis in the 

 sputum. Friedlander believed that the bacillus described by him was 

 the specific cause of croupous pneumonia; but in 129 cases examined by 

 Weichselbaum this bacillus was found in only 9; of 70 cases examined 

 by Wolf only 3 showed the presence of Friedlander's pneumobacillus. 

 It is evident, therefore, that though this micro-organism may be con- 

 cerned in the production of certain forms of the disease, it is not the 

 specific cause of croupous pneumonia. The cases which are due 

 primarily to the pneumobacillus are distinguished, according to Weichsel- 

 baum and Netter, by their peculiarly malignant type and by the viscidity 

 of the exudate produced. This bacillus is also probably concerned, 

 primarily or secondarily, under certain circumstances, in the production 

 of pleurisy, abscess of the lungs, pericarditis, endocarditis, otitis media, 

 and meningitis, in all of which diseases it has at times been found to 

 be present. 



