64 ANILIN COLOURS GIVING INDIRECT NUCLEAR STAINS. 



When the clearing is accomplished to your satisfaction, 

 mount in damar or balsam, or stop the extraction of the 

 colour if clove oil have been used by putting the sections 

 into some medium that does not affect the stain (xylol, cedar 

 oil, &c.). 



100. General Results. The results depend in great measure 

 on the previous treatment of the tissues. If you have given 

 them a prolonged fixation in Flemming's strong chromo-aceto- 

 osmic mixture, and have washed out after staining with acid 

 alcohol and cleared with clove oil, you will get, with some 

 special exceptions, nothing stained but nucleoli and the 

 chroinatin of dividing nuclei, that of resting nuclei remaining 

 unstained. If you have given a lighter fixation, with 

 Flemming's weak mixture or some other fixing agent not 

 specially inimical to staining, and have washed out after 

 staining with pure alcohol, you will get the chromatin of 

 resting nuclei stained as well. With some of these stains 

 Victoria, for instance it is easy to get cytoplasm stained, 

 in a lighter tone than the nuclei, by merely washing out 

 lightly. 



It may be noted here that most of the dyes discussed in 

 this chapter give a stain of a somewhat dead or dull quality, 

 so much so that in some cases chromosomes and nucleoli come 

 out quite opaque. Safranin and anilin green, however, do 

 not do this, but leave the structures beautifully transparent. 

 This is an advantage with thick sections, and sometimes for 

 other reasons ; but this transparency of the elements is un- 

 fortunately favorable to the production of diffraction lines 

 which may be a hindrance to good definition in delicate 

 work. 



101. Safranin one of the most important of these stains, 

 on account of its great power, brilliancy, and superior per- 

 manence in balsam, and also on account of the divers degrees 

 of electivity that it displays for the nuclei and other consti- 

 tuent elements of different tissues. 



The great secret of staining with safranin is to get a good 

 safranin. It is needful here to insist most urgently on what 

 was said above, 94, sub. finem. Before thinking of working 

 with this important reagent, you should go to Griibler or to 

 Miinder and order the safranin you want, specifying whether 



