1 2 IN TROD UCTIOtf. 



in the center of the slide in a drop of water, 

 grasp the edge of the cover firmly with the fine 

 forceps, breathe on the under side, hold it in a slanting 

 position over the drop of water, place the lower edge 

 in the edge of the drop, and lower it gradually on the 

 water. The condensed moisture of the breath insures 

 more ready contact of the water with the cover, and 

 lowering the cover slantwise gives opportunity for the 

 escape of air from under it. 



If air bubbles appear in the mounting, they are due 

 to one of two reasons : either (i) the cover glass was 

 not clean, or (2) it was dropped instead of being low- 

 ered to the slide. Of these the first is the more com- 

 mon cause of air bubbles. They may sometimes be 

 removed by lifting one edge of the cover with a needle, 

 while the other is prevented from slipping, and then 

 lowering again. Sometimes it will be necessary to 

 remove the cover, clean and replace it. 



If the bubbles appear in the specimen itself, they are 

 probably caused by allowing the section to dry partly 

 before mounting. They may usually be removed by 

 taking off the cover and treating the specimen with 

 alcohol. 



The worker should not be content to let bubbles 

 remain. 



Another difficulty is sometimes encountered, when 

 it is attempted to mount several sections under the 

 same cover, in the floating out of one or more. This 

 is usually due to an excess of water. The remedy is to 

 take up the cover, absorb some of the water with filter 

 paper, and re-cover. 



After covering specimens, soak up the superfluous 



