396 ADDITIONS. 



To observe the typical changes in indirect nuclear 

 division, a larval salamander 2 to 3 c.m. long, 

 hardened in Flemming's mixture, may be conveni- 

 ently taken, divided into two or three pieces, and 

 then cut longitudinally. 



Staining medullated fibres in grey substance. 

 Weigert's method. 



Prepare 



(1) Mordant solution. An aqueous solution of normal 



cupric acetate saturated in the cold, and add an 

 equal volume of water. 



(2) Staining solution. Dissolve 1 gram of hsema- 



toxylin in 10 c.c. of absolute alcohol, add 90c.c. 

 of water and 1 c.c. of a cold saturated aqueous 

 solution of lithium carbonate (or sodium car- 

 bonate). 



(3) Decolourizing solution. Dissolve 2J grams of 



potassium ferricyanide and 2 grams of borax 

 in 200 c.c. of water. 



Sections are placed in the cupric acetate in the warm 

 for a day, washed in water, and transferred to hsema- 

 toxylin for two hours to a day. The sections, now 

 quite black, are washed with water and placed in the 

 potassium ferricyanide solution for a few minutes to 

 two hours, until the grey substance becomes of a 

 light tint ; if the decolourization is rapid, it is better 

 to dilute with water the ferricyanide solution ; the 

 sections are then well washed with water, treated 

 with alcohol, and mounted in Canada balsam. 



Another method of decolourizing is given by Pal; the sections 

 after having been stained, are washed with water containing 

 a little lithium carbonate, placed in '25 p. c. potassium per- 



