NEUROLOGICAL METHODS. 401 



Acid. Oxalic, pur. . . . . 1*0 



Potassium Sulphite* (Kalium Sulfuro- 



sum [S0 3 K 2 ]) . . . . 1-0 

 Aq. Best 200'0 



In a few seconds the grey substance of the sections is 

 decolourised, the white matter remaining blue. The sections 

 should now be well washed out, and may be double-stained 

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

 acetic- acid-carmine. 



For further details as to the somewhat elaborate minutiae 

 of the process see the papers quoted, or BEHRENS, KossEL r 

 and SCHIEFFERDECKER'S Das MikrosJcop, i, p. 199. 



PAL'S process gives more brilliant results than that of 

 Weigert, the ground of the preparations being totally colour- 

 Jess. But it has a defect ; it is less certain, or, to put it in 

 another way, less easy to control. The differentiation is 

 more energetic and rapid than is desirable. The whole 

 process of differentiation only lasts some seconds ; evidently,, 

 then, nn error of judgment of only a few seconds may 

 entirely vitiate the result. 



WEIGERT (f/rgebnisne, vi, p. 21) considers that for very 

 thick sections the process is superior to his own. But it is 

 not so safe for very fine fibres, and is not applicable to his 

 collodion series method ; each section must be treated sepa- 

 rately. 



MAECUS stains by the Pal method sections of material hardened in- 

 formalin, as described 692. 



See also MARINA, 692. 



GUDDEN (Neurol. Centralb., xvi, 1897, p. 24) makes celloidin sections of 

 material hardened in 5 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 haematoxylin a few drops of dilute nitric acid (MiNNicn). 



TSCHEENYSCHEW and KABUSIN (Zeii. f. wiss. Mik., xiii, 1896, p. 354), 

 stain for twenty-four hours in the haematoxylin of KULTSCHITZKY. 



DOLLKEN (Zeit.f. wiss. Mik., xv, 4, 1899, p. 444) stains for four or five 

 days in the haematoxylin cold, then for two hours at 37 C., washes for six 

 to eight hours in spring water, and for a quarter of an hour in distilled 

 water containing 2 to 3 drops of caustic potash per litre, differentiates in 

 the permanganate until the undeveloped non-medullated tracts (the method 



* Not " sulphide," as erroneously given in MEBCIEB'S Les Coupes de 

 Systeme Nerveux Central, p. 190. 



26 



