BACTERIA IN CROUPOUS PNEUMONIA. 



397 



glass preparation is placed for twenty-four hours in a solution of 

 gentian violet and acetic acid, containing fifty parts of a concentrated 

 alcoholic solution of gentian violet, one hundred parts of distilled 

 water, and ten parts of acetic acid. The stained preparation is 

 washed for a minute or two in a one-per-cent solution of acetic acid, 

 dehydrated with alcohol, cleared up with oil of cloves or cedar, and 

 mounted in balsam. The bacillus is quickly stained in dried cover- 

 glass preparations by immersion in aniline- water-gentian-violet solu- 

 tion (two or three minutes). The stained preparation should be de- 

 colorized by placing it in absolute alcohol for half a minute, and then 

 washed in distilled water. 



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 stab 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 Fia * 89 ~ Friedl5nder1s 



y bacillus; stab culture in 



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

 tively low temperatures 16 to 20 C. but is more at 16 - 18 - (Baumgar- 

 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- 



