﻿310 The Philippine Journal of Science wu 



the tip of the pipette, into which it enters by capillarity. A 

 sterile portion of the cover is brought over the tip, and the 

 organism is discharged on it by air pressure through a rubber 

 tube held in the mouth of the operator. The whole process is 

 carried out under the microscope, under the highest powers if 

 desired. 



The pipette is the most essential part of the apparatus, and 

 the governing of its movements is a vital part of the technique. 

 There are several ways of holding and manipulating the pipette, 

 and for the sake of convenience each will be described as a 

 separate method. 



METHOD I 



In this method the pipette is manipulated by means of a 

 special holder clamped directly to the stage of the microscope 

 or to a metal plate fastened to the underside of the stage. 



APPARATUS 



The apparatus needed are the following: 



1. A compound microscope furnished with a mechanical stage, 

 preferably one allowing wide movement in both directions. 



2. The pipette holder, preferably the type with three move- 

 ments." 



3. A specially constructed moist chamber. 



4. Large cover glasses to fit the top of the chamber. 



5. A piece of rubber tubing about 70 centimeters long and 

 about 6 millimeters in diameter. 



6. Pieces of glass tubing, 15 to 20 centimeters in length, about 

 4 to 5 millimeters in diameter, and with a lumen about 3 milli- 

 meters in diameter. 



7. A microburner with a very small flame. 



Some parts of the above apparatus are here described in 

 detail : 



There are two types of pipette holder: the one having move- 

 ments, accurately governed by screws, in three directions of 

 space; the other having but two such movements mechanically 

 governed, the movements to the right or left of the observer 

 being accomplished by sliding the pipette in a groove with the 

 fingers. The three-movement holder is preferable, as the ad- 

 ditional movement makes the technique easier for the learner, 

 saves time in adjusting the pipette, and enables the worker to 



' Pipette holders may be obtained from the University of Kansas, 

 Lawrence, Kansas, U. S. A. 



