THE MICROSCOPE AND MICEOSCOPIC METHODS 33 



wire, which has been properly sterilized, one can easily remove 

 portions from a culture of bacteria, or from a fluid in which 

 bacteria are supposed to be present. The rod in which the wire 

 is fixed should be held between the thumb and forefinger of the 

 right hand like a pen. 



Glass Pipettes. — Sterile glass tubes drawn out to form slender 

 capillaries, Pasteur pipettes, are very convenient instrumehts 

 for handling bacteriological materials, and, for many kinds 

 of work, really indispensable. They serve nearly all the pur- 

 poses of the platinum wire and are capable further of use to 

 transfer large quantities of fluid without contamination. They 

 are also especially useful in collecting material from patients 



""T-^pffrer 



c 



d 



Pig. 21.— Drawn-out tube pipettes of Pasteur, a. Plugged, sterile tube as 

 kept in stock; b, the same heated at x in blast-lamp and drawn out; then sealed at 

 *; c and d, completed pipettes; e, the same with bulb. {After Novy.) 



and at autopsy. Each pipette is sterilized and discarded after 

 use.. * 



These pipettes are made by cutting glass tubing of a suitable 

 size, diameter 3 mm. to 9 mm., into pieces from. 20 to 40 cm. in 

 length. The cut ends are smoothed in the flame. In the tubes 

 of larger caliber it is well to make a constriction about 5 cm. from 

 each end. Each end is plugged with cotton. The tubes are then 

 sterilized by dry heat. By heating the middle of the tube in 

 a blast lamp or over a large Bunsen flame, the glass may be 



