WEIGERT'S MYELIN STAIN 511 



nervous system. As a result of some chemical reaction between myelin 

 and a chrome salt, the myelin is fixed so that it does not dissolve in alco- 

 hol and ether, and at the same time is mordanted so that it stains deeply 

 with haematoxylin. 



1. Fix in a 10 per cent, aqueous solution of formalin for several days 

 to several weeks, or indefinitely. Use a large quantity of fluid; change 

 at the end of 24 hours and thereafter whenever it becomes cloudy. 



2. Cut the tissue into pieces not over i cm. thick, and place in a 2.5 

 per cent, aqueous solution of potassium bichromate renewed each day 

 for 3 or 4 days; then in a 5 per cent, solution renewed each day for 3 to 

 4 days. 



3. Wash in running water for 24 hours (large pieces several days). 



4. Transfer the tissues to the following solution (Weigert's second 

 mordant) for 24 to 48 hours. 



Acetate of copper 5.0 gm. 



Acetic acid, 36 per cent, solution 5.0 c.c. 



Fluorchrom 2.5 gm. 



Water 100.0 c.c. 



Boil the fluorchrom and water in a covered dish; turn off the gas and 

 add the acetic acid and then the acetate of copper. Stir until the latter 

 dissolves, and cool. 



5. Wash in running water 24 hours or longer. 



6. Dehydrate in graded alcohols and imbed in celloidin. Cut sec- 

 tions 20-25 ft thick. 



7. Stain sections for 12 to 24 hours in: 



Ripened 10 per cent, solution of haematoxylin in absolute alcohol 10 



Saturated aqueous solution of lithium carbonate i 



Water '. 90 



The haematoxylin is kept as a stock solution and combined with the 

 carbonate of lithium and water at the time of using. Beautiful results 

 may also be obtained by staining over-night or longer in Weigert's iron- 

 haematoxylin (p. 502). 



8. Wash in water. 



9. Differentiate in the following solution: 



Borax 2.0 



Potassium ferricyanide 2.5 



Water 100.0 



It is advisable to dilute this solution with i or 2 volumes of water. 

 After the first staining method, the gray substance of the sections appears 

 yellow; after the iron-has matoxylin it is colorless. 



10. Wash in running water 4 hours to over-night. 



u. 95 per cent, alcohol, 3-5 hours (may be left over-night). 



12. Fresh 95 per cent., 5 minutes. 



13. Clear in carbol-xylol. 



14. Mount in xylol damar. 



