492 APPENDIX. 



II. REAGENTS USED IN STAINING. 



ALUM CARMINE. 



Preparation. Dissolve 200 grms. ammonia-alum in water : boil 

 10-20 minutes with excess of carmine : filter : make up 

 to 1 litre with water : add a few drops of carbolic acid to 

 preserve from mould. 



Use. Stain for hardened tissues. It may be diluted with 

 4 times its bulk of water or less. 



BORAX CARMINE (Grenadier's). 



Preparation. Dissolve 125 grms. carmine and 20 grms. borax 

 in 500 c.c. water : add 600 c.c. 70 per cent, alcohol : allow 

 to stand two or three days : filter. 



Use. Stain for tissues which have been hardened. May be 

 used warm (50 C.) or cold. The tissues should afterwards 

 be treated with acid alcohol. For staining objects which 

 are to be mounted whole, such as chick embryos, it should 

 be diluted with several times its bulk of 40 per cent, 

 alcohol, and the treatment with acid alcohol should be 

 prolonged. 



ACID ALCOHOL. 



Preparation. To 100 c.c. of 70 per cent, alcohol add 25 c.c. 

 hydrochloric or nitric acid. 



Use. For differentiating the parts of stained specimens, and 

 for removal of surplus stain. 



PICRO CARMINE. 



Preparation. Dissolve 10 grms. carmine in 40 c.c. strong 

 ammonia and 2 litres water. Add 50 grms. picric acid. 

 Shake well a few minutes : allow to stand : and decant. 

 Allow to stand a few days, stirring occasionally. Evapo- 

 rate to dryness over a water-bath. To every 2 grms. of dry 

 residue add 100 c.c. water. 



Use. Stain. It may be used with advantage for specimens 

 hardened with osmic acid or otherwise. Subsequent 



