﻿IX. B, 4 Barber: The Pipette Method 331 



fine capillary, and this is cut into any desired lengths in a sterile 

 Petri dish — 1 centimeter is a convenient length. An ordinary 

 pipette is made, moistened in sterile fluid, and the capillary made 

 to cling to it as shown in fig. 10. Care must be taken not to get 

 liquid into the short capillary. The pipette is adjusted in the 

 usual manner. The capillary is partially filled by touching a 

 small hanging drop of broth or other fluid medium, and then the 

 organism is drawn in by capillarity. The pipette is then turned 

 and the capillary deposited on the underside of the cover in a 

 dry area or in a drop of fluid, as desired. I have grown yeast 

 cells in a capillary so narrow that multiplication was possible 

 only in the form of a chain. Plague bacilli in the center of such 

 capillaries have shown involution forms not observed in the 

 control outside. 



Again, an ordinary pipette may be drawn to a very fine capil- 

 lary, so fine that human red blood corpuscles must bend at the 

 edges in order to lie in it. Organisms may be taken up in 

 this capillary and the capillary 

 flattened against the cover and 

 observed under the oil immer- 

 sion while still attached to the 



pipette. It is then possible to 



discharge all or a part of the 



contents of the pipette into a ^^°- l"- ^ capUlary tube in position for 

 , . , mi J . 1 taking up isolated organisms. 



hangmg drop. The tip may be 



sealed by touching it to a hanging drop of sterile vaseline under 

 the cover, then removed from the holder, and placed in the in- 

 cubator. It may later be brought under observation again. 

 The sealed tip may be broken off, under microscopical control, 

 by means of a separate, coarse-pointed pipette held in a second 

 holder clamped on the microscope. The organism may then be 

 discharged into a hanging drop. 



INOCULATION INTO ANIMALS 



The isolated organism, or any small number desired, may be 

 taken up and immediately inoculated into an animal, subcu- 

 taneously, intravenously, or intraperitoneally. A pipette of 

 slightly different construction is used for this purpose. Tub- 

 ing of tough glass, not too thin walled, is drawn out into a capil- 

 lary slightly thicker than that of an ordinary pipette. The tip 

 is made and bent as usual, although the bent portion should 

 have as a base some of the thicker part of the capillary. The 

 pipette is supplied with salt solution or broth from a test tube. 

 Care should be taken to avoid breaking off too much of the tip 



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