﻿334 



The Philippine Journal of Science 



1914 



dropper is filled and the water in it heated slightly over the 

 flame. The temperature of the water is gauged by the tem- 

 perature of the room. One can usually judge the condition of 

 the moisture film with the naked eye. As a rule, it is best not 

 to use the outer third of the cover for isolation. By keeping this 

 outer third of the cover supplied with hanging drops of agar 

 or broth, the moisture of the other two-thirds of the box may 

 be increased. Very constant conditions of moisture may be 

 obtained within a long, narrow area on the cover inclosed by a 

 barrier of agar. It is important to have the cover well sealed 

 to the edges of the chamber in order to avoid convection currents. 

 Drafts of air on the laboratory table should be avoided, especially 

 those blowing toward the open end of the chamber. 



One may protect the open end of the box by a piece of 

 moistened filter paper provided with a slit for the capillary por- 

 tion of the pipette. A hood of moistened blotting paper {H, fig. 

 1) is still more convenient. A slight modification of the isolating 

 chamber will assist in protecting the under surface of the cover 

 in special experiments. A glass strip is cemented to the slide 

 just outside of the chamber in such a way as to form a groove 

 into which a piece of moist blotting paper may be inserted in 

 an upright position, or the blotting paper may be slipped into 

 the chamber and held upright by the sides. This method of 

 protection leaves less working room for the pipette, but this 

 difficulty may be avoided by bending the end of the pipette into 



the form shown in fig. 11. Here 

 the tip of the pipette is just 

 above the line of the capillary, 

 and this arrangement allows one 

 to work with the capillary of the 

 pipette above the barrier of 

 blotting paper. 



I have used an isolating chamber, a portion of which is wholly 

 sealed by means of a trap filled with water or mercury, t (fig. 

 12). The pipette capillary is bent into the form illustrated in 

 the figure and adjusted into the chamber. If a capillary of hard 



Fig. 11. A pipette constructed for use above 

 a barrier of blotting paper. 



Fig. 12. Special isolatins chamber in longitudinal section. The chamber b is closed at the side 



by the trap t and partition p. 



