CH. X] 



MOUNTING MICROSCOPIC OBJECTS 



329 



2. The object is arranged as desired in the center of a clean slide 

 on the centering card (fig. 192). 



3. A drop of the mounting medium is put directly upon the object 

 or spread on a cover-glass. 



4. The cover-glass is put on the specimen with fine forceps (fig. 

 190), but in no case does one breathe on the cover as when media 

 miscible with water are used. 



5. The cover-glass is pressed down gently. 



6. The slide is labeled. 



7. The preparation is catalogued and safely 

 stored ( 526). 



512. Example of mounting in balsam by 

 desiccation. Find a fresh fly, or, if in winter, 

 procure a dead one from a window sill or a 

 spider's web. Remove the fly's wings, being 

 especially careful to keep them the dorsal side 

 up. With a camel's hair brush remove any 

 dirt that may be clinging to them. Place a 

 clean side on the centering card, then with 

 fine forceps put the two wings within one of 

 the guide rings. Leave one dorsal side up, 

 turn the other ventral side up. Spread some 

 Canada balsam on the face of the cover-glass 

 and with the fine forceps place the cover upon 

 the wings (fig. 190). Probably some air- 

 bubbles will appear in the preparation, but 

 if the slide is put in a warm place these will soon disappear. Label, 

 catalogue, etc. 



513. Mounting in resinous media by a series of displacements. 

 - For examples of this see the procedure in the paraffin and in the 

 collodion methods, Ch. XL The first step in the series is dehydration; 

 that is, the water is displaced by some liquid which is miscible both 

 with the water and the next liquid to be used. Strong alcohol (95 % 

 or stronger) is usually employed for this. Plenty of it must be used 

 to displace the last trace of water. The tissue may be soaked in a 

 dish of the alcohol, or alcohol from a pipette may be poured upon it. 



FIG. 195. CONTAINER 

 FOR CANADA BALSAM, 

 GLYCERIN JELLY, ETC. 



Cover The glass cover 

 to keep out dust and pre- 

 vent evaporation. 



Rod The glass rod for 

 transferring the contents 

 of the container to the 

 slide. 



