PNEUMOBACILLUS. 459 
of this bacillus from that of the bacillus aérogenes, 
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 ex- 
amined 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-serum abundant, grayish-white, 
viscid masses are developed. The growth on potato 
is luxuriant—a thick, yellowish-white, glistening layer 
rapidly covering the entire surface. Milk is not coagu- 
lated. ndol is produced in bouillon or peptone solu- 
tions. Fermentation of milk-sugar and glucose is 
caused. Growth occurs at 16° to 20° C., but is more 
rapid at 37° C. 
Pathogenesis. Friedlander’s bacillus is pathegenia 
for mice and guinea-pigs, less so for dogs, and rabbits 
are apparently immune. In Friedlinder’s experiments 
mice proved to be particularly susceptible. These 
animals, when pure cultures of the bacillus are in- 
jected through the thoracic wall into the tissue of the 
lung, invariably succumb to the disease. On autopsy 
the pleural cavities are found to contain a sero-puru- 
lent fluid, the lungs are intensely congested, and in 
places show limited areas of red hepatization; the 
spleen i is considerably enlarged, and bacilli are present 
in the lungs, the pleuritic fluid, and the blood. In 
guinea-pigs which are killed by the inoculation similar 
appearances are observed. 
Friedlinder’s bacillus has been found in man, not 
only in patients suffering from croupous pneumonia 
and other respiratory diseases, but also in healthy indi- 
