ZOOLOGY AND BOTANY, MICBOSCOPY, ETC. 159 



nerve-fibres of tlie white and grey matter a brilliant red, tbe other 

 parts varying in tint to blue. This was much praised by all who 

 used it as an exceptionally excellent method, but is now superseded 

 by a new stain, which Prof. Weigert * considers to be still better, 

 and which, according to all accounts, is specially valuable as being 

 extremely simple and easy, and, above all, unfailing. 



The first solution used consists of hgematoxylin 0*75 to 1-0, 

 alcohol 10 "0, and water 90*0, the mixture being boiled and left to 

 stand several days before being used. 



In this solution sections, cut with alcohol and not water, and 

 hardened in Miiller's or Erlicki's f fluid, are allowed to remain for 

 1-2 hours at a temperature of 35°-45° C. The sections are now 

 coal black. 



After washing with water they are placed in a solution of borax 2 • 0, 

 potassium ferricyanide 2*5, and water 100*0, until the white is dif- 

 ferentiated from the grey matter, the latter becoming indistinctly 

 yellow, while the former remains black. They can then be washed, 

 treated with alcohol, xylol, and Canada balsam in the usual way. 



W. T. Councilman,^ writing of this process, says that any one 

 using it for the first time will be struck with the richness of the net- 

 work of nerve-fibres in the grey matter of the cord. What was 

 formerly spoken of as gelatinous substance or neuroglia will be found 

 to be mostly nerve-fibres. They are not visible under ordinary cir- 

 cumstances, because the intermediate substance stains as intensely 

 as the axis-cylinders. At first sight it will appear that the axis- 

 cylinders are stained, but closer inspection with high powers will 

 show that these are really unstained, and the white substance of 

 Schwann has taken on the colour. In the middle of the bright red 

 or purple spots which represent the cross sections of nerve-fibres, 

 the unstained axis cylinder can be seen. It is in all respects just the 

 opposite to the ordinary staining of carmine and h£ematoxylin. The 

 method is also invaluable iu the pathology of the cord in tracing 

 degenerated nerve-tracts. 



Method for Displaying the Course of the Fibres in the Central 

 Nervous System.§ — S. Freud proposes the foUowiug method for this 

 purpose : — 



Thin sections of brain hardened in bichromate of potash, after 

 washing to free them from the alcohol with which the razor has been 

 moistened, are placed in a watch-glass with 1 per cent, solution of 

 gold chloride and left for 3-5 hours. They are then removed with 

 a clean fragment of wood, washed in distilled water, and placed in a 

 solution of caustic potash (1 part potash to 5 or 6 water) for about 

 three minutes. The superfluous potash is removed by placing the 

 sections on filter paper, and they are then placed in 10-12 per cent, 

 sodium^ potash, where they acquire a red colour; in 5-15 minutes 

 the staining is complete. 



* Fortschr. d. Med., 1884, pp. 113, 190. 



t Potassium bichromate 2-5; copper sulphate 0*5; distilled water lOO-O. 



t Amer. Mon. Micr. Journ., v. (1884) pp. 201-3, 



§ Arch. f. Anat. u. Phys., 1884, pp. 453-60. 



