MICROSCOPICAL EXAMINATION OF BACTERIA 71 



7. Three aluminium rods (Fig. 63), each about 25 

 cm. long and carrying a piece of 0.015 gauge platino- 

 iridium wire 7.5 cm. in length. The end of one of the 

 wires is bent round to form an oval loop, of about i 

 mm. in its short diameter, and is termed a loop or an 

 oese; the terminal 3 or 4 mm. of another wire is flat- 

 tened out by hammering it on a smooth iron surface 

 to form a " spatula"; the third is left untouched or is 

 pointed by the aid of a file. These instruments are 



FIG. 63. Ends of platinum rods, a, loop; b, spatula; c, needle. 



used for inoculating culture tubes and preparing speci- 

 mens for microscopical examination. 



The method of mounting these wires may be de- 

 scribed as follows: 



Take a piece of aluminium wire 25 cm. long and 

 about 0.25 cm. in diameter, and drill a fine hole com- 

 pletely through the wire about a centimetre from one 

 end. Sink a straight narrow channel along one side 

 of the wire, in its long axis, from the hole to the nearest 

 end, shallow at first, but gradually becoming deeper. 



On the opposite side of the wire make a short cut, 

 2 mm. in length, leading from the hole in the same 

 direction. [The use of a fine dental drill and small 

 circular saw, worked by a dental motor facilitates the 

 manufacture of these aluminium handled instruments.] 



Now pass one end of the platinum wire through the 

 hole, turn up about 2 mm. at right angles and press 



