512 HISTOLOGY 



Pal's Modification of Weigert's Stain. The tissue is fixed, mordanted 

 and imbedded as directed in i, 2, 3 and 6 above. Sections may be very 

 much thicker. 



7. Sections are placed for several hours in a \ per cent, aqueous solu- 

 tion of chromic acid, or for a longer time in a 2.5 per cent, solution of 

 potassium bichromate. (May be omitted.) 



8. Stain for 24 to 48 hours in: 



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



Water ' 90 



9. Wash in water plus i to 3 per cent, of a saturated aqueous solution 

 of lithium carbonate until the sections appear of a uniform deep blue 

 color. 



10. Differentiate for 20 seconds to i minute in a \ per cent, aqueous 

 solution of potassium permanganate. 



11. Place for a few seconds in the following solution, until the gray 

 substance is colorless or nearly so: 



Oxalic acid i 



Potassium sulphite i 



Water 200 



12. Wash in water. 



Repeat steps 10, 11 and 12 until the differentiation is complete. Then 

 wash 4 hours or longer in running water. 



13. 95 per cent, alcohol, 3 to 5 hours. 



14. Fresh 95 per cent., 5 minutes. 



15. Carb.ol-xylol. Mount in xylol damar. 



Golgi's Method for the Impregnation of Nerve Cells. This method 

 depends on the formation of a fine precipitate in certain tissue elements 

 or in pre-existing spaces when the tissues are treated with a solution of 

 potassium bichromate and then with a solution of silver nitrate or 

 mercuric bichloride. The value of the method lies on the fact that it 

 picks out here and there a cell and stains it with its processes more 

 or less completely. This same fact renders the method very uncertain. 

 Of the several modifications of this stain, only one the so-called 

 rapid method is here given. 



1. Pieces of fresh tissue about 5 mm. thick are placed for 3 to 8 days 

 in the following solution: 



Osmic acid, i per cent, solution i part 



Bichromate of potassium, 3 . 5 per cent, solution 4 parts 



2. Transfer to a large quantity of 0.75 per cent, solution of silver 

 nitrate for 2 or 3 days. 



Keep the tissues in the dark during treatment with both fluids. 

 The length of time the tissues should remain in the first solution 

 depends on the elements it is desired to impregnate. 



