154 SPECIAL BACTERIOLOGY 



be allowed to work a considerable time. The reaction with Gram's 

 method is negative. Sections may be stained with Loffler's methyleiie 

 blue solution. 



Biological Characters. The comma bacillus grows on all the 

 ordinary nutrient media, also in the absence of oxygen (facultative 

 anaerobe), but according to recent investigations the oxygen must not 

 be completely absent. The culture media must possess a decided alkaline 

 reaction, as the comma bacillus is very sensitive to the smallest quantity 

 of acid. 



The minimum temperature at which development takes place is 

 8 C., optimum 30 to 40 C. 



On Gelatine Plates the development takes place best at 22 C., and 

 in twenty-four to thirty hours, when examined under a low power, small 

 yellowish-white granular knotty colonies with uneven rough edges are 

 present, the surface looks as if it were covered with little fragments of 

 broken glass ; while the colony has a shining appearance when lique- 

 faction commences. An ill-defined halo is first seen to surround the 

 granular colony, which exhibits a peculiar roseate hue by transmitted 

 light. 



In Gelatine Stab Cultures development occurs along the line of inocula- 

 tion, but the liquefaction occurs first only at the surface ; on the second 

 day, at 22 C., a short funnel is formed with a very narrow mouth, the 

 upper portion of which contains air, and below this a whitish viscid mass. 

 The funnel now increases in depth and diameter, and in four to six days 

 may reach the edge of the test-tube ; in eight to fourteen days the upper 

 two-thirds of the gelatine is liquefied, and in a few weeks the gelatine 

 is completely liquefied. 



On Agar Plates the growth is not so characteristic as with gelatine 

 media ; the surface colonies exhibit a peculiar light greyish-brown trans- 

 parent appearance. 



On Agar Stroke Cultures a greyish-white, moist, shining coating 

 develops. 



Blood Serum is liquefied slowly. 



On Potatoes placed in the incubator a thin semi-transparent brown or 

 greyish-brown layer is developed. In some potatoes no growth takes 

 place, but development takes place if the potatoes are rendered alkaline 

 with a solution of soda, or cooked in a 3 per cent, solution of common 

 salt. 



Milk is a favourable culture medium. 



Bouillon is clouded, and in the majority of cases, when placed in the 

 incubator, a thin membrane forms on the surface of the medium. 



Like most vibrios and spirilla the comma bacillus possesses the 

 peculiarity of being able to multiply very energetically in bouillon 

 reduced with six to eight parts of water. It also develops in 1 per cent. 



