﻿IX, B. 4 Barber: The Pipette Method 345 



dissected, and various other manipulations performed. Either 

 one or both of the pipettes may be provided with mercury and 

 used for cell inoculation. It is better to use hard glass in making 

 fine points for dissection. 



For the dissection of very delicate, soft objects, as blood 

 corpuscles and some protozoans, I have made use of sharp stiff 

 hairs, taken from the body of a house fly, and also of very 

 fine-pointed needle crystals. A pipette with a fairly large open- 

 ing is made, and the hair or crystal drawn partially into it, the 

 thicker end within. The fine point projecting from the tip of 

 the pipette is then used as a probe or dissecting needle. The 

 same pipette may be used as a holder for a considerable variety 

 of these fine tools. 



THE PIPETTE AND ISOLATING CHAMBER USED AS SEPARATE UNITS 



There are some uses of the pipette or of the isolating chamber 

 as separate units which may merit a short description. 



The isolating chamber has been found a very useful adjunct 

 to the microscopist in furnishing a convenient method of examin- 

 ing material in hanging drop. One has only to place with a 

 loop a drop of the material to be examined under the cover 

 glass, and the same cover glass may be used for the examination 

 of many colonies of bacteria, of samples of faeces, of protozoans, 

 or of microscopical plants. If desired, the cover glass with 

 the samples may be sealed on a ordinary moist chamber for 

 further observation. A pipette containing an agglutinating 

 serum or some simple stain may be used in connection with the 

 hanging drops. 



The pipette will often be found convenient in fishing colonies 

 from a plate in which the colonies are too close together to be 

 transferred with the platinum needle. The Petri dish or other 

 plate may be held in a clamp in an inverted position over the 

 stage; where this is not practicable, an area of the medium 

 containing the colonies may be transferred to a large cover and 

 placed over an isolating chamber. 



A straight, fine-pointed pipette provided with a rubber tube 

 may be used for inoculating microorganisms into insects. A 

 point much finer than that of a syringe needle may be made 

 and materials inoculated between the joints of the leg or into 

 any part visible under a hand lens. If a very fine point is 

 needed for inoculations into animals or plants, the pressure 

 apparatus described in connection with the cell injection tech- 

 nique may be" used. In order to gain freedom of movement, 

 the pressure pipette may be suspended by a cord. The raising 



