56 MICRO-CHEMICAL REAGENTS. 



obtained in the market ready prepared. The stain- 

 ing fluid is made by dissolving .35 gm. haematoxy- 

 lin in 10 gm. water. To this are added a few drops 

 of an alum solution (which acts as a mordant in 

 fixing the color), made by dissolving 3 gm. alum in 

 30 gm. water. This makes a beautiful violet fluid, 

 which colors the nucleus deep blue. It is the best 

 staining fluid that is now known for the nucleus. 1 

 Preparations need to lie in it for some time. They 

 may be preserved in glycerine. 



I have used with success the method of staining 

 bacteria first published by Koch. The dried 

 preparation is treated with a concentrated extract 

 of Campeachy-wood in water. After removing the 

 superfluous dye with distilled water, the color is 

 fixed by the use of dilute chromic-acid. The prep- 

 aration can be preserved, after drying, in glycerine 

 or Canada balsam. Cilia and the bodies of the 

 cells are sharply differentiated by this method. 2 

 Koch has later recommended coloring with haem- 

 atoxylin. Staff-shaped bacteria, however, do not 

 color by this substance, according to him. 3 I have 

 however used the haematoxylin tincture with suc- 

 cess even on certain staff-shaped bacteria. After 

 rinsing, my preparations are preserved dry. 



Histologie, p. 103. Robin: Microscope, 1877, p. 250. Bachmann: Dauer- 

 praparate, p. 28. Schmitz : Niederrhein. Gesellsch., Nov. 1879. 



1 Johow: Zellkerne d. hoheren Monocotylen., Diss., Bonn, 1880, p. 9, 

 note. 



2 Koch : Conserviren und Photographiren der Bacterien. Cohn's Beitr. 

 z. Biol. d. Pfl., II., p. 421. 



3 Wundinfectionskrankheiten, 1878, p. 30. 



