BACTERIA IN CROUPOUS PNEUMONIA. 



309 



Biological Characters. This bacillus does not, so far as is 

 known, form reproductive spores ; it is non-motile and does not 

 liquefy gelatin. It is aerobic and a facultative anaerobic. In 

 gelatin stick cultures it presents the "nail-shaped" growth first 

 described by Friedlander, which is not, however, peculiar to this 

 bacillus. The head of the nail is formed by the 

 development around the point of entrance of the 

 inoculating needle of a rounded, white mass hav- 

 ing a smooth, shining surface, and its stem by the 

 growth along the line of puncture. This consists 

 of closely crowded, opaque, white, spherical colo- 

 nies. Gas bubbles sometimes develop in gelatin 

 cultures, and in old cultures the gelatin about the 

 line of growth acquires a yellowish-brown color. 

 The growth in nutrient agar resembles that in 

 gelatin. Upon the surface of blood serum abun- 

 dant grayish- white, viscid masses are developed. 

 Upon potato the growth is abundant, quickly cov- 

 ering the entire surface with a thick, yellowish- 

 white, glistening layer which often contains gas 

 bubbles when the temperature is favorable. Col- 

 onies in gelatin plates appear at the end of twenty- 

 four hours as small, white spheres, which increase 

 rapidly in size, and upon the surface form round- 

 ed, smooth, glistening, white masses of consider- 

 able size. Under the microscope the colonies pre- 

 sent a somewhat irregular outline and a slightly 



& J bacillus; stick culture in 



granular appearance. Growth occurs at compara- gelatin; end of four days 



tively low temperatures 16 to 20 C. but is more * e t n 16 - 18 c ' 



rapid in the incubating oven. The thermal death- 



point, as determined by the writer, is about 56 C. In the ordinary 



culture media it retains its vitality for a long time, and may grow 



when transplanted to fresh culture material after having been pre- 



served for a year or more. At a temperature of 40 C. development 



ceases. 



Pathogenesis. In Friedlander's experiments the bacillus from 

 pure cultures, suspended in water, was injected through the thoracic 

 wall 4nto the right lung of dogs, rabbits, guinea-pigs, and mice. 

 Rabbits proved to be immune ; one dog out of five, six guinea-pigs 

 out of eleven, and all of the mice (thirty-two) succumbed to the 

 inoculation. At the autopsy the pleural cavities were found to con- 

 tain a sero-purulent fluid ; the lungs were intensely congested, con- 

 tained but little air, and in places showed limited areas of red infil- 

 tration ; the spleen was considerably enlarged ; the bacillus was 



