CHAPTER XXXIII. 443 



The 1884 method (Fortschr. d. Med., ii, 1884, pp. 120, 190 ; Ztschr. 

 wiss. Mikr., i, 1884, pp. 290, 564), which depends on the formation of 

 a chrome lake of hsematoxylin, may be considered as superseded. 

 Not so the two others, which depend on the formation of a copper 

 lake in addition to the chrome lake. 



854. WEIGERT'S 1885 Method (Fortschr. d. Med., iii, 1885, p. 236 ; 

 Ztschr. wiss. Mikr., 1885, pp. 399, 484 ; Ergebn. Anat., vi, 1896 

 (1897), p. 10).- -The tissues are hardened in potassium bichro- 

 mate. WEIGERT takes (Ergebn., p. 10) a 5 per cent, solution, and 

 if time is an object hardens in a stove. (Other bichromate mixtures 

 will do, .</., Miiller's, Kultschitzky's, Zenker's ; Erlicki's is not to 

 be recommended.) The tissues are " ripe' for staining when the 

 hardening has been carried to a certain point. They are first 

 yellow, without differentiation of the grey matter from the white ; 

 these are unripe. Later they show the grey matter light brown, 

 the white matter dark brown ; and these are ripe. 



More recently (Ergebn., p. 14) he added to the bichromate solution 

 2 per cent, of chrome alum or of chromium fluoride, which hastens 

 the hardening, so that small specimens become brown and ripe in 

 four to five days, without stoving. 



After hardening, tissues are generally embedded in celloidin and 

 the blocks hardened in the usual way. They are then put for one or 

 two days, in an incubating stove, into a saturated solution of neutral 

 copper acetate diluted with 1 volume of water. By this treatment 

 the tissues become green and the celloidin bluish-green. They may 

 then be kept, till wanted for sectioning, in 80 per cent, alcohol. 



Sections are made, well washed in water, and brought into a 

 stain composed of :- 



Hsematoxylin . . . . . -75 to 1 part. 



Alcohol . . . . . .10 parts. 



Water . . . . . . 90 



Saturated solution of lithium carbonate . 1 part. 



They remain there, for spinal cord, two hours ; for medullary 

 layers of brain, two hours ; for cortical layers, twenty-four hours. 



They are then again well washed with water, and brought into a 

 decolorising solution composed of : 



Borax . . . . . .2-0 parts. 



Ferricyanide of potassium . . . 2-5 ,, 

 Water . . . . . 200-0 



They remain there until complete differentiation (half an hour to 



