726 PROTOZOOLOGY 



6 hours to overnight. Rinse them thoroughly in neutral distilled 

 water and transfer them through the following jars in order (about 

 5 minutes in each): (a) acetone alone; (b) acetone: xylol, 8:2; (c) 

 acetone : xylol, 5:5; (d) acetone : xylol, 2:8; (e) two changes of xylol. 

 The smears are now mounted in cedar wood oil (which is used for 

 immersion objectives) and the preparations should be placed in a 

 drying oven for a longer time than the balsam-mounted prepara- 

 tions. 



Feulgen's nucleal reaction. The following solutions are needed. 



(a) HCl solution. This is prepared by mixing 82.5 cc. of HCl (spe- 

 cific gravity 1.19) and 1000 cc. of distilled water. 



(b) Fuchsin-sodium bisulphite. Dissolve 1 gm. of powdered fuchsin 

 (basic fuchsin, diamant fuchsin or parafuchsin) in 200 cc. of distilled 

 water which has been brought to boiling point. After frequent shak- 

 ing for about 5 minutes, filter the solution when cooled down to 50°C. 

 into a bottle and add 20 cc. HCl solution. Cool the solution further 

 down to about 25°C. and add 1 gm. of anhydrous sodium bisulphite. 

 Apply stopper tightly. Decolorization of the solution will be com- 

 pleted in a few hours, but keep the bottle in a dark place for at least 

 24 hours before using it. 



(c) Sulphurous water. 



Distilled or tap water 200 cc. 

 10% anhydrous sodium 



bisulphite 10 cc. 



HCl solution (a) 10 cc. 



Feulgen's reaction is used to detect thymonucleic acid, a constitu- 

 ent of chromatin. By a partial hydrolysis, certain purin-bodies in the 

 acid are split into aldehydes which show a sharp Schiff's reaction 

 upon coming in contact with fuchsin-sodium bisulphite. Thus this 

 is a reaction, and not a staining method. Smears fixed in sublimate- 

 acetic or Schaudinn's fluid are brought down to running water, after 

 being placed for about 24 hours in 95% alcohol. Immerse them in 

 cold HCl for one minute, then place them in HCl kept at 60°C. (over 

 a microburner or in an incubator) for 5 minutes, quickly immerse in 

 cold HCl. After rapidly rinsing in distilled water, place the smears 

 in solution (b) for 30-minutes to 3 hours. There is no overstaining. 

 The smears are then washed in three changes (at least 2 minutes in 

 each) of solution (c). Wash them in running water for 30 minutes. If 

 counterstaining is desired, dip in 0.1% light green solution and rinse 

 again in water. The smears are now dehydrated through a series of 

 alcohol in the usual manner and mounted in Canada balsam. 



