80 THE MICROSCOPIST. 



it. Then pour in the balsam at one end, the slide being 

 inclined so that the turpentine may run out at the other. 

 Lay the cover on one edge of the cell and gradually lower 

 it till it lies flat. In this way air may be excluded. 



The solution of balsam in chloroform needs no heat, 

 and has little liability of air-bubbles. 



The excess of balsam round the edge of the glass cover 

 may be removed with a knife and cleaned with turpentine 

 or benzine, etc. 



For animal tissues, the oil of cloves is sometimes used 

 instead of turpentine to increase the transparency, and a 

 wet preparation, as a stained or injected specimen, may 

 be mounted in balsam or Dammar by first placing it in 

 absolute alcohol to extract the water, then transferring 

 to oil of cloves or turpentine, and lastly, to the balsam. 

 In a reverse order, a specimen from balsam may be cleaned 

 and mounted in fluid. 



Mounting in Fluid is necessary for the preservation of 

 the most delicate tissues and such as may be injured by 



FIG. 38. 



Spring Clip. 



drying. Glycerin is perhaps the most generally useful 

 fluid. (See Preservative Fluids, page 73.) 



For mounting in fluid, it is safer to have a thin cell of 

 varnish prepared first than to risk the running in of the 

 cement under the cover, as will be likely to occur other- 

 wise. 



The air-pump is sometimes needed in mounting in fluid 

 to get rid of air-bubbles. A spring clip (Fig. 38) is also 



