METHODS USED IN CULTIVATION OF BACTERIA 



147 



scendants of a single bacterium of the original mixture, are carried 

 over to the fresh medium. 



Esmarch Roll Tubes. 1 A simple method of obtaining separate colo- 

 nies is that devised by von Esmarch and known as " roll-tube " cultiva- 

 tion. Tubes of melted gelatin are inoculated with various dilutions of 

 the bacterial mixture and, while still liquid, are laid in an almost horizon- 



FIG. 31. STREAK PLATE. 



tal position upon a block of ice, which has been grooved slightly by 

 means of a test tube filled with hot water. The test tube containing the 

 gelatin, after being placepl in this groove, is rapidly revolved by passing 

 the fingers of the right hand across it, while its base is carefully 

 steadied with the left hand. If the revolving is carried out with 



Esmarch, Zeit. f. Hyg., i, 1886. 



