328 



MOUNTING MICROSCOPIC OBJECTS 



[CH. X 



(C) Balsam preparations may be sealed with shellac as soon as they 

 are prepared, but it is better to allow them to dry for a few days. 

 One should never use a cement for sealing preparations in balsam or 

 other resinous media if the solvent of the cement is also a solvent 

 of the balsam, etc. Otherwise the cement will soften the balsam and 

 finally run in and mix with it, and partly or wholly ruin the prepa- 

 ration. Shellac is an excellent cement for 

 sealing balsam preparations, as it never runs 

 in. Balsam preparations are rarely sealed. 

 509. Example of mounting in glycerin 

 jelly. For this select some stained and 

 isolated muscular fibers or other suitably pre- 

 pared objects ( 514-519). Arrange them on 

 the middle of a slide, using the centering 

 card, and mount in glycerin jelly as directed 

 in 507. Air bubbles are not easily removed 

 from glycerin jelly preparations, so .care 

 should be taken to avoid them. 



510. Mounting objects in resinous media. 



- While the media miscible with water offer 

 FIG. 104. SMALL SPIRIT , r i 



LAMP USED AS A CON- manv advantages for mounting animal and 



TAINER FOR GLYCERIN, vegetable tissues, the preparations so made 



liable to deteriorate. In 



BALSAM, ETC. 



are liable to deteriorate. In many cases, 

 also, they do not produce sufficient transparency to enable one to use 

 high enough powers for the demonstration of minute details. 



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 drying or desiccation (511), and (B) 

 by successive displacements ( 513). 



511. Order of procedure in mounting objects in resinous 

 media by desiccation: 



i. The object suitable for the purpose (fly's wings, etc.) is thor- 

 oughly dried in dry air or by gentle heat. 



