CULTURAL TECHNIQUE 31 



All trouble can be avoided by the use of the needle handle 

 devised by Kavetiel. An aluminum rod of 2.5-3 mm. diameter 

 is procured and cut into pieces 150-200 mm. long. In the end 

 of each rod a hole is drilled with a small drill. The platinum 

 wire is inserted 'into the hole and the end of the rod ham- 

 mered lightly so as to close the hole about the wire. The 

 aluminum rod may be inserted in a piece of glass tubing, so 

 that it can be more easily handled. 



Each student should have two inoculating needles, (1) one 

 in which the wire is straight and is used for puncture inocu- 

 lations, (2) and another in which a loop is formed at the free 

 end, which is used in making transfers from liquid cultures. 

 The loop should be made around an eight-penny common 

 nail which has a gauge of 10 J. The needle must always be 

 heated to red heat for its entire length, and the lower part 

 of the glass rod be passed through the flame several times in 

 order to sterilize the needle before use. The wire should be 

 allowed to cool for a few seconds before it is used. After 

 using, it must be again heated to red heat to sterilize it before 

 being laid down. The habit of heating immediately before 

 and after using must be acquired, so as to become practically 

 an involuntary act. If this habit is acquired, much subse- 

 quent trouble will be avoided. The lower part of the glass 

 should not be soiled with media. A "loopful" means all the 

 fluid the loop can hold. This should be a biconvex mass, not 

 merely a film covering the lumen of the loop. 



Exercise. Each student will prepare a needle and a standard loop. 



Plate cultures. In testing the purity of a culture or in the. 

 isolation of the forms present in a mixture of bacteria plate 

 cultures must be prepared. This is done, in case a culture is 

 to be tested for its purity, by melting three agar or gelatin 



