550 APPLICATION OF METHODS OF BACTERIOLOGY 



track are much more pronounced than is the case with the 

 "comma bacillus." 



Its growth on agar-agar is rapid; after twenty-four to 

 forty-eight hours a grayish deposit appears which has a 

 tendency to become yellowish with age. 



On potato at 37 ° C. its growth is seen as a moist, coffee- 

 colored patch, surrounded by a much paler zone. The 

 whole growth is so smooth and glistening that it has some- 

 what the appearance of being varnished. 



In bouillon it quickly causes opacity, with the ultimate 

 production of a delicate pellicle upon the surface. 



It causes liquefaction of blood-serum, the liquefied area 

 being covered by a dense, wrinkled pellicle. 



When grown in peptone solution it produces indol and 

 coincidently nitrites, so that the rose-colored reaction 

 characteristic of indol is obtained by the addition of sul- 

 phuric acid alone. The production of indol by this organism 

 is usually greater than that common to the comma bacillus 

 under the same circumstances. 



In milk it causes an acid reaction with coagulation of the 

 casein. The coagulated casein collects at the bottom of the 

 tube in irregular masses, above which is a layer of clear 

 whey. If blue litmus has been added to the milk, the color 

 is changed to pink in from twenty-four to thirty hours, 

 and after forty-eight hours decolorization and coagulation 

 occur. The clots of casein are not re-dissolved. After about 

 a week the acidity of the milk is at its maximum, and the 

 organisms quickly die. 



It causes the red color of the rosolic-acid-peptone solution 

 to become very much deeper after four or five days at 37° C. 



It does not cause fermentation of glucose with production 

 of gas. 



