376 APPENDIX 



solution of paraffin in carbon bisulphide and thence to paraffin. Bisulphide of 

 carbon has the disadvantage of foul odor and inflammability but does not seem to 

 render tissues brittle and difficult to section as does xylol. 



NEUROLOGICAL STAINING METHODS. 



Neuropathology practically dates from the introduction of Marchi's method of 

 staining in 1885. 



Ordinary osmic acid stains both normal and pathological fat. With Marchi's 

 method only the oleic acid of fatty degeneration is stained. 



The method is not useful until three or four days have elapsed from the onset 

 of the condition causing the degeneration and it is applicable for only three or four 

 months because by that time phagocytes have taken up the pathological fat which 

 is stained in the Marchi method. The Weigert method is the one to use after a 

 period of three or four months. In Weigert's stain only the normal myelin sheath 

 is stained and the lack of staining of myelin sheaths in degenerated areas is the basis 

 of the stain. For demonstrating axonal reactions or other degenerative changes 

 in nerve cells, as shown by bulging of the concave sides of the cells, eccentric nucleus 

 and granular appearance of the tigroid bodies, Nissl's method is the best. 



For neuroglia fiber staining Mallory's phosphotungstic acid haematoxylin is to 

 be recommended. 



I. For Marchi's Method. Small pieces of nerve tissue are hardened in Miiller's 

 fluid for seven to ten days and are then transferred to a mixture of two parts Miiller's 

 fluid and one part of a i% osmic acid solution and should remain in this mixture 

 for about seven days. The tissue thus treated is run through alcohols and imbedded 

 in paraffin in the usual way. 



II. For Weigert-Pal Method. Thin slices of tissue are fixed in 10% formalin 

 in about four days. The tissue should then be transferred to 5% potassium bichro- 

 mate for about twelve days. The tissue is then imbedded and sections cut. If 

 only recently mordanted these sections may be at once stained with Weigert's 

 haematoxylin for twelve to twenty-four hours (10 c.c. ripened 10% solution haema- 

 toxylin in absolute alcohol and 90 c.c. water). Wash in water to which about 2% 

 of a saturated solution of lithium carbonate has been added. Now differentiate 

 from one-half to five minutes in 1/4% solution of potassium permanganate until 

 the gray matter looks a brownish-yellow. Next treat sections with oxalic acid 

 i gram, potassium sulphate i gram and water 200 c.c. until the gray matter is 

 almost colorless. This takes only a few seconds. Wash in water, pass through 

 alcohols and xylol and mount in balsam. 



III. For Nissl staining either thionin or Giemsa staining is satisfactory. 



IV. For neuroglia fiber staining use Mallory's Phosphotungstic acid haematoxylin. 



Take of haematein ammonium, o.i gram. 



Water, 100.0 c.c. 



Phosphotungstic acid crystals (Merck) 2.0 grams. 



Dissolve the haematein in a little water with the aid of heat, and add it after it is 

 cool to the rest of the solution; no preservative is required. If the solution stains 

 weakly at first, it may be ripened by the addition of 5 c.c. of a 1/4% aqueous 



