PATHOGENIC SPIRILLA. 



595 



depth, and at the bottom of which is seen the colony in the form of 

 a small, white mass ; as a 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 

 have a more or less irregular outline, 

 the margins being rough and uneven; 

 the texture is coarsely granular, and the 

 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, 



FIG. 176. Colonies of the cholera 

 spirillum; a, end of twenty hours ; 6, 

 end of thirty hours; c, end of forty- 

 eight hours; d, after liquefaction of 

 the gelatin. (Flugge.) 



FIG. 177. Spirillum choleras Asiaticse; a, one day old; b. three days old; c, four days old; d, five 

 days old; e, seven days old; /, 10 days 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 



