Collecting and Handling 43 



cultures the late Dr. A. Brooker Klugh* devised a plunger pipette that 

 is a great help in picking out cells of the smallest sizes. We copy in full 

 his description and figure of it. 



"This instrument (Fig. 39) consists of: (1) a piece of thin, soft glass tubing 

 drawn to a capillary tube at one end; (2) a glass plunger drawn from a piece of 

 glass rod to sufficient fineness to fit the capillary tip, and with a flattened knob at 

 the other end; (3) a piece of rubber tubing which is placed so as to project beyond 

 the glass tube. 



"In the figure the capillary tube is, for the sake of clearness, shown as relatively 

 coarse, but in practice this tube should have an inside diameter of 80 micra or less. 



"These parts are so adjusted that the end of the plunger inside the capillary is 



Plwger. W*w 



Plwupr 



Head . 



Fig. 39. — The plunger-pipette. After Klugh. 



about 1 mm. from the end of the capillary, while the knob rests against the rubber. 

 This is accomplished by inserting the plunger (which should be made with the fine- 

 drawn portion longer than required), and cutting off the part which projects through 

 the capillary, then making the fine adjustment by moving the rubber slightly 

 upwards. 



"The manner of using this instrument is as follows: A drop or two of water 

 containing some of the organisms it is desired to isolate is placed on a slide, the 

 organism located, and examined with the 4 mm. objective and a xio, or higher, 

 ocular. The desired organism is then located under the 16 mm. or 8 mm. objective. 

 The pipette is held with the thumb and second finger just in front of the rubber, 

 while the plunger-head is pressed with the first finger so that the end of the plunger 

 projects from the tip of the capillary The end of the plunger is brought against the 

 organism and the pressure of the first finger released, when the resiliency of the 

 rubber withdraws the plunger and the organism is drawn into the end of the 

 capillary. (If other organisms, or debris, lie close against the desired organism, they 

 may be knocked away by shooting the plunger in and out by the pressure of the 

 forefinger.) The organism is then transferred in the pipette to a hollow-ground 

 slide containing a drop of the culture medium, and is ejected by a pressure on the 

 plunger-head. It is then examined under high power to see that it is absolutely free 

 from foreign organisms, picked up with the pipette as before, and transferred to the 

 culture-vessel. 



"The chief advantages of this instrument are: 



"1. The plunger does away with the drawing in of undesirable material by 

 capillarity. 



"2. The plunger may be employed to clear other organisms away from the organ- 

 ism to be isolated. 



"3. The instrument is quick and certain in operation. 



"4. It is easily portable. 



"5. It is simple and requires no special attachments. 



* /. Roy. Micr. Soc. for 1922, p. 2b^ 



