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 aérobic and a facultative anaérobic. 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 a ee ee 
granular appearance. Growth occurs at compara- gelatin; end of four days 
tively low temperatures—16° to 20° C.—butis more # 16°18 C. 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- 
