7O APPENDIX TO PART I. 



exclude dust, until all water is evaporated, and the 

 balsam becomes perfectly hard on cooling. It is 

 then dissolved in enough pure benzole to make a 

 thin solution, and filtered. The usual directions 

 advise subsequent evaporation to the consistency 

 of cream, but it may be satisfactorily employed for 

 most purposes in a much more fluid form. Glass 

 stoppers, which are always advisable for reagent 

 bottles, are indispensable for bottles intended to 

 hold this or Dammar. Sections may be mounted 

 in this solution directly from benzole, or from either 

 of the commonly used clearing fluids clove oil or 

 turpentine. W. T.] 



Only such things as contain little water should 

 be mounted in balsam. If the objects are delicate 

 and contain much water, they must be anhydrated 

 in absolute alcohol, or dried in the air, and when 

 it is necessary they should be cleared in clove oil 

 before mounting. Although balsam preparations 

 cannot dry up, or move about after the medium 

 has once hardened, they need to be sealed, as 

 a jar may at any time loosen the cover. Such a 

 partial or complete loosening is easily detected by 

 the appearance of Newton's rings. 1 



1 Literature of Mounting Media. Dippel . Das Mikroskop, I., p. 470, 

 et seq. Schacht: Mikroskop, 1855, p. 28. Sanio : Bot. Zeitung, 1863, p. 

 359. Koch: Conn's Beitr. z. Biol. d. Pfl., Bd. II., p. 407. Bachmann: 

 Dauerpraparate, 1879. Frey: Mikroskop, pp. 122, 125. Harting: Mikro- 

 skop, III., p. 409. Pelletan : Le Microscope, 1876, p. 178, et seq. 



