172 MOUNTING AND LABELING [CH. VII 



By using sufficient care almost any tissue may be mounted in a resinous 

 medium and retain all its details of structure. 



For the successful mounting of an object in a resinous medium it must in 

 some way be deprived of all water and all liquids not miscible with the resinous 

 mounting medium. There are two methods of bringing this about : (A) By dry- 

 ing or desiccation {\ 256), and (B) by successive displacements (§ 258). 



Fig. 142. Small spirit lamp modified into a balsam 

 bottle, a glycerin or glycerin -jelly bottle, or a bottle 

 for homogeneous immersion liquid. For all of these 

 purposes it should contain a glass rod as shown in the 

 figure. By adding a small brush, it answers well for 

 a shellac bottle also {See Fig. 170). 



\ 256. Order of Procedure in Mounting Objects in Resinous Media by 

 Desiccation : 



1. The object suitable for the purpose (fly's wings, etc. ) is thoroughly dried 

 in dry air or by gentle heat. 



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

 centering card (Fig. 138). 



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. 136), 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 gentl} 7 . 



6. The slide is labeled {\ 308). 



7. The preparation is cataloged and safely stored {\ 309, 311 ). 



I 257. 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 slide 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. 136). Probably some air-bubbles 

 will appear in the preparation, but if the slide is put in a warm place these will 

 soon disappear. Label, catalog, etc., (1307-311). 



$ 25S. Mounting in Resinous Media by a Series of Displacements. — For ex- 

 amples of this see the procedure in the paraffin and in the collodion methods 



