190 METHODS OF USING CULTURE MEDIA 



solid media. The platinum loop is of lighter wire, 0.018 inch. 

 The loop in the end is conveniently made by twisting the 

 wire around the lead of an ordinary lead-pencil. The "loop 

 needle" (Fig. 126) is most used in transferring liquid media. 

 On account of the high price of platinum the author has 

 substituted "nichrome" wire for student use. This is 

 stiffer, not so easily made into loops and breaks out of the 

 rods more easily. The latter defect is remedied by inserting 

 the wire into the end of an aluminum rod. The low cost, 

 less than one-twentieth of platinum, justifies its use. 



Fig. 125. — Straight needle. 



Fig. 126.— Straight and loop needles. 



Fig. 127. — Pasteur flask — "balloon pipette." 



Sterile graduated pipettes varying in capacity from 1 cc 

 graduated in hundredths, upward, permit the transfer of 

 definite amounts of Uquids. Large quantities are conve- 

 niently transferred by means of Pasteur flasks (Fig. 127). 

 The details of inoculation are best derived from laboratory 

 practice. 



