﻿IX, B, 4 Barbsr: The Pipette Method 313 



pipette holder. It may be fastened to the stage by means of 

 small clamps. 



The moist chamber (fig. 3) is made by fastening strips of 

 glass to a slide with Canada balsam or any convenient cement. 

 It is well to cement an additional strip on the slide at the open 

 end s. This serves to hold water in the bottom of the chamber 

 and to strengthen the whole apparatus. Pieces of slides may be 

 used in making the chamber, but it is better to have glass of 

 somewhat greater thickness — about 1.5 millimeters. A very 

 convenient size for the moist chamber is 70 millimeters long, 

 35 wide, and 28 high. If the mechanical stage in use will not 

 admit so broad a chamber, one of the width of an ordinary 

 slide may be used. The narrow chamber is more readily kept 

 moist, the narrower cover glass suited to it is more easily cleaned, 

 and the preparations grown on this cover glass are more easily 

 stained and mounted than is the case with the larger cover glass. 

 However, the broader chamber gives much more working room, 



and for most routine work will 



be found more convenient. It / 

 is advisable to make two or three j 

 moist chambers at a time. One '-^ 

 narrow and two broad ones will 



give a good working outfit. Fig. 3. isolating chamber, p. lining of 



Temporary isolation chambers !''°"'"^, ^^p"/ /; ^'^^ =*"p *°' '"'^'°- 



^ '' ing water in bottom. 



may be made of wood or strong 



pasteboard. A convenient way is to modify a wood or paste- 

 board box, cement it to a slide, and make it partially water- 

 proof at the bottom with Canada balsam or any convenient 

 substance. 



The height recommended is chosen because it gives working 

 room for the pipette without being so far from the stage as 

 seriously to diminish the light. It will be found very advan- 

 tageous to replace the ordinary substage condenser with one 

 which will focus the light at a point somewhat above the stage. 

 This is especially adapted for work with the oil-immersion 

 lens or other high powers. The moist chamber is lined on the 

 sides and end with filter paper, p (fig. 3), in order to furnish 

 a larger moist surface. The upper edges of the isolating 

 chamber should be even and smooth, so that the cover glass 

 may be easily sealed on them. 



The cover glass should be large enough to seal well to the 

 sides of the chamber and to reach to the ends. It should be 

 of such thickness as to permit safe handling, while not so thick 



