58 A MANUAL OF BACTERIOLOGY 



A good medium for the growth of chromogenic 

 microbes is made of ground rice. The late Dr. 

 Isidor Soyka's formula for the preparation of this 

 medium is as follows : 1 grammes of ground rice, 

 15 cc. of milk, and 5 cc. of neutral beef bouillon. 

 These ingredients are made into a paste, which is 

 transferred to covered glass dishes or small flasks. 

 The dishes or flasks are then sterilised (in the steam 

 steriliser) for half an hour on three successive days. 



Bread-paste is also used as a medium for the 

 cultivation of microbes. It is prepared in the fol- 

 lowing way : The crumb of a loaf is broken into 

 small pieces, dried in an oven, and rubbed through 

 a fine sieve. The finely-divided bread is then placed 

 in a sterilised flask, to the depth of half an inch, 

 sterilised water being added until the bread is 

 thoroughly moistened. After replacing the cotton- 

 wool plug the flask (or flasks) is sterilised in the 

 steam steriliser for the same length of time as rice- 

 paste. The flask containing either bread- or rice- 

 paste can be reversed, and is readily inoculated by 

 means of a platinum needle. 



To inoculate solid culture media ' the test-tube or 

 flask is held inverted in the left hand, and the plug 

 of cotton wool is twisted once or twice in the mouth 

 of the test-tube to break down any adhesions 

 between it and the neck of the vessel. If the plug 

 is at all dusty, it is well to singe the surface by 

 passing it rapidly through a flame before removing 

 it from its position. The plug is removed and held 

 between two of the unoccupied fingers of the left 

 hand, great care being taken that no part of the 



