WEIGERT-PAL 525 



By means of Weigert's methods only the myehn slieaths of 

 normal nervc-fibrcs are stained, whilst those of degenerated 

 tracts are of a paler colour and, if the degeneration is sufficiently 

 old, they may even be stainless. Sec also § 1081. 



P. Meyer {Neurol, CentrbL, xxviii, 1909, p. 353) hardened formol 

 material in 5 per cent, potassium bichromate at 37° C. for from two 

 weeks to several months, changing the mordant frequently, until the 

 white matter was brown. After imbedding in celloidin, sections 50 [x 

 thick are put first into Weigert's gliabeize for twenty-four hours at 

 37° C, then washed in 70 per cent, alcohol and stained for twenty-four 

 hours in Weigert's iron haematoxylin. They are differentiated first 

 with diluted borax-ferri cyanide solution and then, if necessary, with a 

 stronger solution. 



For Sheldon's modification, which is also based on a formalin fixation 

 see Folia NeurobioL, viii, 1914, p. 1. 



MODIFICATIONS OF WEIGERT'S METHOD 



1058. Pal's Method {Wien. med. Jahrb., N.F. i, 1886, p. 619 ; 

 Ztschr. wiss. Mikr., vi, 1887, p. 02 ; Med. Jahrb., N.F. ii, 188T, 

 p. 589). One proceeds as in Weigert's process, but omitting 

 the copper bath. After staining in the ha-matoxylin solution, the 

 sections are washed in water (if they are not stained of a deep 

 blue a trace of lithium carbonate must be added to the water). 

 They are then brought for 15 to 20 seconds into 0-25 per cent, 

 solution of potassium permanganate, rinsed in water, and brought 

 into a decolourising solution composed of : — 



Oxalic acid . . . . . 1-0 grm. 



Potassium sulphite (SO.^Ko) . . . 1"0 ,, 



Dist. water ..... 200-0 c.c. 



In a few seconds the grey substance of the sections is decolourised, 

 the white matter remaining blue. If the differentiation is not 

 complete the whole process can be repeated a second time, and 

 so on. The sections should now be well washed out, and may be 

 counterstained with Magdala red or eosin, or (better) with picro- 

 carmine, acetic acid carmine, or alum carmine. 



Pal's process gives brilliant results, the ground of the prepara- 

 tions being totally colourless. Weigert {Ergebn. Anat., vi, 1896, 

 p. 21) considered it superior to his own for thick sections, but 

 not so safe for very fine fibres. 



Marcus stains by the Pal method sections of material hardened in 

 formalin. 



GuDDEN (Neurol. CentrbL, xvi, 1897, p. 24) makes celloidin sections of 

 material hardened in 5 to 10 per cent, formol followed by alcohol, treats 

 them for ten hours with 0-55 per cent, chromic acid, rinses with water, 

 and treats with 80 per cent, alcohol ; then stains by the method of Pal. 

 adding to the htematoxylin a few drops of dilute nitric acid (Minnicii). 



TscnERNYSCiiEW and Ivarusin {Ztschr. wiss. Mikr., xiii, 1896, p. 354) 

 stain for twenty-four hours in Kultschitzky's haematoxylin. 



