246 PRACTICAL HISTOLOGY [XXXI 



The piece of tissue is cut, either superficially imbedded 

 in paraffin (p. 58), or imbedded in celloidin, or frozen. 



The sections are placed in a few c.c. of the hsematoxylin 

 solution for 5 hours to a day at the room temperature, and for 

 about an hour in the warm. 



If the tissue has been kept in alcohol, and the chromic salts 

 extracted, the sections are placed for a day in 2 p.c. potassium 

 bichromate, and washed in water before being stained. 



The sections are washed in water containing a little lithium 

 carbonate and placed 



(a) in *25 p.c. permanganate of potash for 20 sees, to 1 

 minute according to the rate of decolourization, washed and 

 placed in 



(6) a few c.c. of the oxalic decolourizing fluid for a few seconds 

 to a minute till the grey substance is of a light grey tint ; the 

 same fluid should not be used for more than a few sections. 



The sections are then well washed in running water, best till 

 next day, dehydrated and mounted ; before dehydrating they 

 may if desired be stained with alum carmine or picrocarmine. 



Modification by Kutschitzhy and Wolters. 



The following mixture is required : 1 gram hsematoxylin dissolved 

 in abs. alcohol ; 100 c.c., 2 p.c. acetic acid. 



The sections (in celloidin) are placed in the warm (45 C.) for a day 

 in the haematoxylin fluid, put for a second or two in Muller's fluid, 

 and differentiated as in Pal's method. 



Staining degenerating fibres. (Marchi's method.) The 

 piece of central nervous system is placed in Miiller's fluid or in 

 2 p.c. potassium bichromate for 10 days to three weeks, the 

 fluid in this case not being changed ; slices a few millimetres 

 thick are then cut and placed for one to two weeks in a mixture 

 of equal parts of Miiller's fluid and 1 p.c. osmic acid. The 

 pieces may be cut frozen, but they are apt to be brittle. 



