PREPARATION OF CULTURE MEDIA 15 



the mouth of the tube with cotton-wool and sterilize on three 

 successive days. 



INOCULATION OF CULTURE MEDIA 



The method in which this is done varies greatly according 

 to the end in vie-w, and variations of the process now to be 

 described will be mentioned under their appropriate headings. 

 We will suppose that we have to examine a specimen of pus, 

 and wish to make a stroke culture on agaf and a stab culture 

 in gelatin. The following must be at hand : 



1. The pus. 



2. A sloped agar tube and a stab gelatin tube. 



3. A Bunsen burner or a spirit-lamp with a tall flame. 



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 



FIG. 4. PLATINUM NEEDLES. 



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 J- 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 being subsequently twisted round a French 

 nail or other suitable object. 



