SECTION THREE 



acetic acid before mounting. The fluid takes from one to two weeks 

 or even longer to set, after which time the coversUps should be 

 ringed with a waterproof cement and ringed with a layer of 

 Canada balsam in benzene, or Laktoseal can be applied immedi- 

 ately. 



DOETSCHMAN'S GUM CHLORAL MOUNTANT AND 



STAIN 



This is a modification, containing basic fuchsin, of Berleze's 

 fluid. 



This valuable reagent is used in entomology for killing, fixing, 

 dehydrating, clearing, staining and mounting specimens in one 

 operation. Highly chitinized specimens should be treated with 

 10% potassium hydroxide from sixteen to twenty-four hours, 

 then washed well in water before mounting directly into a drop 

 of Doetschman's fluid on a slide. For permanent mounts the 

 preparations should be placed in the oven at 37-50° C. from six 

 to twenty-four hours. Ring the slides with a waterproof cement. 



Reference: Gatenby & Beams (1950), p. 207. 



FARRANTS' MEDIUM 



Refractive index i -432 



This consists of a viscous solution of gum arable in a mixture 

 of glycerine and water, together with a preservative, usually 

 arsenic or phenol, although neither of the latter can be relied 

 upon to prevent the growth of some species of air-borne micro- 

 organisms that bring about the decomposition of this mountant. 

 It is a very old mounting medium, having been devised by 

 Farrants about eighty years ago, and which was, until a generation 

 or so ago, extensively used for preparations stained with Sudan 3 

 and other fat stains of the same group. At the present time, 

 however, it seems to have fallen out of favour. 



GLYCERINE 



Used as an aqueous mounting medium for temporary prepar- 

 ations. Only the purest neutral glycerine should be used. 



517 



