WEIGERT 523 



1056. 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 

 bichromate. 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, e.g. 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 imbedded 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 : — 



Haematoxylin .... 0-75 to 1 part. 

 Alcohol . . . . .10 parts. 



Water 90 „ 



Saturated solution of lithium car- 

 bonate ..... 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 wuth water, and brought into 

 a decolourising 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 several hours), and are then well washed with water (running, 

 or changed several times), dehydrated, and mounted in balsam. 

 They may be previously counterstained, if desired, with alum 

 carmine. 



The method is applicable to the study of peripheral nerves as 

 well as to nerve-centres, and also the study of lymphatic glands, 

 skin (see Schiefferdecker, Anat. Anz., ii, 1887, p. 680), bile 

 capillaries, and other objects. 



The process is applicable to tissues that have been hardened in 

 alcohol or in any other way, provided that they be put into a solution 



