PATHOGENIC SPIRILLA. 595 
depth, and at the bottom of which is seen the colony in the form of 
asmall, white mass; asa result of this the plates on the second or 
third day appear to be perforated with numerous small holes ; later 
the gelatin is entirely liquefied. Under 
a low power the young colonies, before 
liquefaction has commenced, present a 
rather characteristic appearance ; they 
are of a white or pale-yellow color, and 
Fic. 176.—Colonies of the cholera have a more or less irregular outline, 
ee a ane margins being rough and uneven; 
end of thirty hours; c, end of forty- . 
eight hours; d, after liquefaction of the texture is coarsely granular, and the 
chee ie neese surface looks as if it were covered with 
, little fragments of broken glass, while 
the colony has a shining appearance ; when liquefaction commences an 
ill-defined halo is first seen to surround the granular colony, which 
by transmitted light has a peculiar roseate hue. In stab cultures in 
nutrient gelatin development occurs all along the line of inoculation, 
a 6 c d e il 
Fig. 177.—Spirillum cholere Asiatic; a, one day old; b, three days old; c, four days old; d, five 
days old, e, seven days old; f,10days old. From photographs by Koch. 
but liquefaction of the gelatin first occurs only near the surface ; on 
the second day, at 22° C., a short funnel is formed which has a 
comparatively narrow mouth, and the upper portion of which con- 
tains air, while just below this is a whitish, viscid mass ; later the 
funnel increases in depth and diameter, and at the end of from four 
to six days may reach the edge of the test tube; in from eight to 
fourteen days the upper two-thirds of the gelatin is completely lique- 
fied. Owing to the slight liquefaction which occurs along the line of 
growth during the first three or four days, the central mass which 
