1 4 IN TROD UCTION. 



after a few hours. Specimens may be mounted directly 

 from alcohol or water in glycerine, but the saving in 

 time will not be material, unless it is known that the 

 specimens are good, before mounting. Care must be 

 taken that the glycerine does not overspread the cover, 

 which, under such condition, must be taken off and 

 cleaned. Most specimens may remain in glycerine any 

 length of time without deterioration, and will become 

 clearer and clearer all the time. Care must be taken to 

 keep the specimens thus preserved free from dust. 

 They must be handled cautiously, lest the cover be 

 shoved off. If desired, specimens which have been 

 preserved in glycerine, may be permanently mounted, 

 by simply running a ring of shellac cement around the 

 cover. 6 



The greatest care must always be exercised to pre- 

 vent reagents from coming in contact with the stand 

 of the microscope or the lenses, as most of them attack 

 the lacquer of the brass work, and some the brass. 

 The chief danger arises from a failure to remove the 

 excess of the reagent, which then collects at the lower 

 edge of the slide when the microscope is used in an 

 inclined position, and runs off on the stage. Sulphuric 

 acid behaves in the same way even when the excess 

 is once removed, if it is allowed to remain any length 

 of time, because it absorbs moisture from the air. 



Boiling specimens in the potassic chlorate solution 

 should not be done in the same room with the micros- 

 cope as the liquid and its fumes are intensely corro- 

 sive. 



6 For directions for making this cement, see Am. Mo. Mic. Jour., v t 

 (1884), p. 131. Similar cements may be bought. 



