106 BACTERIOLOGICAL LABORATORY TECHNIC 



by simply inoculating the media with some pus or blood containing 

 them, by means of a sterile pipette or platinum needle. Bouillon 

 may be thus inoculated, as may any of the media, and other cultures 

 may be made from these by sterilized needles. But such cultures 

 are made up of colonies of different sorts of bacteria some patho- 

 genic, some non-pathogenic, etc. To separate the various bacteria 

 so that they will grow in isolated groups, is a comparatively easy 



FIG. 29. Colonies in gelatine plate showing how they may be separated and 

 the organisms isolated. (Williams.) 



matter, and is accomplished in several ways. The simplest is to 

 employ several tubes of agar or blood serum. Over the surface of 

 each of these, a platinum loop containing pus, or other matter, is 

 rubbed successively. These tubes are then incubated. After a 

 few hours, the first one exhibits a copious growth of many different 

 kinds of bacteria growing confluently together, from which it is im- 

 possible to isolate any pure cultures. The second tube is less covered 

 with bacteria, while the third, instead of containing a mass of bac- 



