THE CENTRAL NERVOUS SYSTEM. 221 



TECHNIQUE. 



Transverse Sections of the Cord. A perfectly fresh 

 human cord should be freed from its dura mater, divided 

 into short segments, and well hardened in Miiller's fluid. 

 After imbedding in celloidin, thin transverse sections 

 from the lumbar region are stained by Weigert's haema- 

 toxylin method. 



This method of staining is as follows : The sections 

 are placed in an aqueous solution of neutral cupric 

 acetate diluted with an equal bulk of water, for twenty- 

 four hours ; they are then washed in pure water and 

 placed in the following staining fluid : 



Haematoxylin crystals ..... I grm. 



Alcohol, 97 % . . . . . . 10 c.c. 



Water ........ 90 c.c. 



This mixture is boiled and allowed to cool, then i c.c. 

 of a cold saturated aqueous solution of lithium carbonate 

 is added. The sections remain in this fluid for two 

 hours at the ordinary room temperature ; they are then 

 removed, washed well in water, and placed in the follow- 

 ing bleaching fluid : 



Potassium Ferricyanide . . . . 2.5 grms. 

 Sodium Bi-borate . . . . 2.0 grms. 



Water ....... 200. c.c. 



When placed in this fluid, the sections give off clouds 

 of brownish color, and they remain in it until the gray 

 matter becomes of a distinct yellow color and the white 

 matter bluish black. From one half to one hour is 

 required for bleaching. After the bleaching is complete, 



