﻿352 



The Philippine Journal of Science 



1914 



or slightly less. Immediately before turning the point, dip the 

 loop wholly in the ice water. Unless there is a partial vacuum 

 in the capillary at the moment of bending, the heated air may 

 expand and burst through the softened glass. One may inspect 

 the point with a hand lens or under the low power before turning 

 it, but the loop should not be left long out of the ice water while 

 the point is still sealed. The pipette is now ready for use and 

 is to be adjusted in the holder. As soon as the tip is brought 

 near the edge of the cover glass, the cup C should be brought 

 into place and raised so as to immerse the loop in the ice water. 

 The mercury is under great pressure at room temperature, and 

 may break the pipette if it becomes warm while the tip is still 

 sealed. The final adjustments can be made with the loop in the 

 cup. The cup should be so adjusted in the sleeve that when it 



is racked down to its fullest 

 extent the bottom of the loop 

 will just clear the water in the 

 cup. 



The point should now be ad- 

 justed to the center of the high- 

 power field. The tip should be 

 broken off under the high power, 

 and great care must be taken 

 to avoid breaking it prema- 

 turely. It is best to bring the 

 tip into the hanging drop near 

 its edge, but at a little distance 

 below the cover. If left too 

 near the glass, it may be broken 

 by a slight bending of the cover 

 during the focusing with the oil immersion. Sometimes it is 

 more convenient to adjust it under the low power just beneath a 

 small droplet of water, or any object easily recognized, and then 

 lower it slightly. The object is then focused under the oil- 

 immersion lens, and the tip is raised into view. The inoculation 

 should be done under high power. An oil-immersion lens of 

 deep focus is by far the best for this work. 



The tip, still closed, is now in focus under the high power. 

 The end should be opened by pressing it very gently against the 

 cover and moving the mechanical stage slightly. By varying 

 the pressure on the cover glass, the amount broken off and the 

 size of the opening can be regulated. The size must depend on 

 the substance to be inoculated. If liquids, only the smallest 



Fia. 19. Various types of tips used in cell 



injection. 

 (From The Journal of Infectious Diseases.) 



