﻿324 The Philippine Journal of Science mt 



readily found in this way, the pipette may be slipped in and out 

 or moved back and forth until the tip comes into view. It is 

 important to have the tip at a safe distance from the cover, 

 because it is more liable to be broken with these less exact adjust- 

 ments than is the case when the pipette holder is used. 



The tip may now be brought to the center of the field or to a 

 I)oint which corresponds with the center of the high-power field. 

 The finer in-and-out adjustment may be made by slipping the 

 tube with the fingers held in contact with the glass and with the 

 top of the pillar of the dissecting microscope. The fine adjust- 

 ment to and from the observer may be done accurately by sus- 

 pending a pencil pendulum-wise from the fingers and Very gently 

 tapping the end of the arm of the dissecting microscope on the 

 one side or the other, as the case may require. 



The high power is adjusted as in the first method, and further 

 adjustments to the center of the field are made by tapping the 

 arm of the holder for one direction and moving the nose piece of 

 the microscope for the other. Considerable right-and-left adjust- 

 ment may be obtained by the nose piece alone without materially 

 interfering with the illumination or definition. In some micro- 

 scopes it may be necessary to loosen, temporarily, the clip fixing 

 the position of the nose piece. 



The better the focusing apparatus of the simple microscope, 

 the better the results obtained. I have found no difficulty in 

 isolating very small motile bacteria under the %2 oil-immersion 

 lens by this method, and persons who have had no previous ex- 

 perience in the isolation of microorganisms by any method have 

 succeeded in isolating blood corpuscles or bacteria after less than 

 an hour's practice. The adjustments once made, the technique 

 is nearly as easy as with the holder; the method may be used 

 with one type of compound microscope as well as with another. 

 But the greater amount of time and care required for adjusting 

 new pipettes make this method less suitable than the first for one 

 who is doing an extended series of selections or inoculations. 

 Further, the second method is less suited than the first for 

 dissection under the microscope, inoculation into cells, or for 

 some other special applications of the technique to be mentioned 

 later. 



METHOD III 



In the third method of isolation, all mechanical holders are 

 dispensed with and the pipette is held in the fingers of the 

 right hand. The moist chamber is supplied with drops of 

 sterile broth and of the bacterial mixture, as in the other 



