METHODS OF USING CULTURE MEDIA 177 



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. 127) 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 to some extent 

 by imbedding the wire only slightly for about one-fourth 



Fig. 126.— Straight needle. 



Fig. 127. — Straight and loop needle-s. 



Fig. 128. — Pasteur flask — ' ' ballon pipette." 



of an inch on the side of the end portion of the rod. The 

 low cost, less than one-twentieth of platinum, justifies 

 its use. 



Sterile graduated pipettes varying in capacity from 1 c.c, 

 graduated in hundredths, upward, permit the transfer of 

 definite amounts of liquids. Large quantities are conven- 

 iently transferred by means of Pasteur flasks (Fig. 128). 

 The details of inoculation are best derived from laboratory 

 practice. 

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