INOCULATION OF CULTURE MEDIA 17 



4. A pair of dissecting forceps. 



5. Platinum needles. Each needle consists of a piece of 

 platinum wire about 3 inches long mounted in the axis of a glass 

 rod about 6 or 8 inches in length. The wire should be just thick 

 enough not to bend too easily. They are easily prepared. The 

 rod is selected, and the length of platinum wire is held in an 

 ordinary pair of forceps. The end of the glass rod is held in the 

 flame until quite soft; the end of the wire is then heated to 

 redness, and pushed into the rod to the depth of about ^ inch, 

 taking care that it is kept in the axis. The whole is allowed to 

 cool, and is ready for use. 



For some purposes we use needles which terminate in a small 

 loop, so that they will retain a drop of fluid. These are prepared 

 in the same way as the straight needles, the free end of the wire 



Fig. 8. — Platinum Needles. 



being subsequently twisted round a French nail or other suitable 

 'object. 



The method of inoculating a culture is as follows : 



1. Hold the culture-tube you are going to inoculate first between 

 the index and middle fingers of the left hand, pointing the mouth 

 of the tube slightly downwards (so that no dust shall drop into 

 it) and to the right. Tubes of solid media should always be held 

 in this position during inoculation ; tubes of liquid media are held 

 in a similar way, but of course their mouths must point upwards. 



2. Put the projecting portion of the cotton-wool plug of the test- 

 tube into the flame so as to singe it ; this is to destroy any germs 

 which may have been deposited upon it from the atmosphere. 



3. Sterilize the points of the forceps by passing them slowly 

 through the flame, and then use them to remove the plug. Place 

 this between the ring and little fingers of the left hand, and put 

 the forceps down. 



