CHAPTER XXXIII. 445 



Later still (Enzyd. mik. Technik., 1903, p. 942) he employed a 

 stain composed of equal parts of (A), a mixture of 4 c.c. of the 

 officinal Liquor ferri sesquichlorati P. G. with 96 of water, and (B), a 

 mixture of 10 c.c. of a 10 per cent, alcoholic solution of hsematoxylin 

 with 90 of 96 per cent, alcohol. The two (A and B) must be mixed 

 immediately before use, and the sections should remain in the stain 

 overnight or longer, then rinsed and differentiated as usual. This 

 has the advantage of demonstrating very fine fibres, and of giving a 

 colourless back ground. 



For difficult objects the differentiating liquid may be diluted with 

 water, and gives better results than dilute acetic or hydrochloric 

 acids or the like, which were formerly recommended. 



By means of Weigert's methods only the myelin sheaths of 

 normal nerve-fibres are stained, whilst those of degenerated tracts 

 are of a paler colour and, if the degeneration is sufficiently old, 

 they may even be stainless. See also 870. 



856. Formol Material (Ergebn. Anat., vi, 1896, p. 14) may be 

 employed if mordanted till brown (four or five days) in 5 per cent, 

 solution of potassium bichromate with 2 per cent, of chromium 

 fluoride. 



I understand from Dr. Perdrau that this method is the most 

 satisfactory of all for routine work, and relatively small pieces ; but 

 particularly for the histopathological investigation of parts of the 

 human spinal cord, medulla oblongata, pons, and midbrain. He 

 generally cuts from material fixed in formalin, for no less than ten 

 days, slices i to J cm. thick, and places them direct in the mordant 

 (potassium bichromate 5 grms., chromium fluoride, 2-5 grms., water, 

 100 c.c.) for five to six days. Eelatively large pieces may be left in 

 the mordant four or five days longer. After a thorough wash in 

 running tap water, he dehydrates and embeds in celloidin. The 

 sections are stained overnight in Kultschitzky's hsematoxylin ( 859) 

 several months old, washed in water, and placed in a bowl of distilled 

 water to which about 2 c.c. of a saturated solution of lithium 

 carbonate have been added. They are stirred about several times 

 and transferred into a fresh bath of the same solution if necessary, 

 until the celloidin is all but colourless. He lastly differentiates, as 

 by Pal's method ( 857), washes, and counterstains either in alum 

 carmine for ordinary work or in an alcoholic solution of eosin if 

 the preparations are to be photographed. 



P. MEYER (Neurol Centrbl, xxviii, 1909, p. 353) embeds formalin 

 material in celloidin and cuts before putting into Weigert's copper fluid. 



