CH. IX ] 



MOL 'NTING IN BALSAM 



257 



'{ 352. Example of Mounting in Glycerin Jelly. — For this select some 

 stained and isolated muscular fibres or other suitably prepared objects. (See 

 under isolation \ 357). Arrange them on the middle of a slide, using the cen- 

 tering card, and mount in glycerin jelly as directed in \ 350. Air bubbles are 

 not easily removed from glycerin jelly preparations, so care should be taken 

 to avoid them. 



\ 353. Mounting Objects in Resinous Media. — While the media tnisci- 

 ble with water offer many advantages for mounting animal and vegetable tis- 

 sues the preparations so made are liable to deteriorate. In many cases, also, 

 thej' 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 resi- 

 nous mounting medium. There are two methods of bringing this about : (A) 

 By drying or desiccation (<S 355), and (B) by successive displacements ($ 356). 



Fig. 203 Fig. 204 



Fig. 203. 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. 



Fig. 204. Capped balsam bottle. This form is more satisfactory than the 

 preceding. (Cut loaned by the Whitall Tatuiu Co.) 



(S 354. 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. 



