XXXI] SPINAL CORD 243 



day in running water, placed for a day in the dark in 30 p.c., 

 50 p.c., 75 p.c. alcohol, then for a week in 95 p.c. alcohol. It 

 is kept till required in 75 p.c. alcohol. (For the treatment when 

 medullated nerve-fibres or neuroglia fibres have to be stained 

 cp. below.) 



On the 2nd or 3rd day after placing in potassium bichromate, 

 the dura mater may be cut open over the anterior and posterior 

 fissures. 



Miiller's fluid may be used instead of potassium bichromate ; 

 and the potassium bichromate may be 3 to 5 p.c. instead 

 of 2 p.c. 



The dura mater should be removed, and the cord cut into 

 segments, the segments being determined by the place of exit 

 of the roots ; in the lower lumbar and sacral region the roots 

 must be carefully followed to their place of exit. The segments 

 are placed in separate bottles. 



The piece to be cut is placed in water for half a day to a 

 day, and the same time in gum ; sections are cut frozen, and 

 left in picrocarmine best perhaps Ranvier's for two or more 

 days in the warm. 



Methods for the Central Nervom System. 



Hardening. Potassium bichromate as given above may be 

 used for all parts of the central nervous system. Erlicki's fluid 

 (p. 300) hardens more quickly, and Miiller's fluid with formol 

 (p. 300) still more quickly. 



The hardening should be carried out in the cold till the fluid 

 has thoroughly penetrated ; it may then be carried out in the 

 warm and thereby much hastened. 



These hardening agents do not allow a staining of the basophil 

 substance ; when this is required in addition to other stains, 

 Marina's fluid (cp. p. 301) or formol alone may be used. Formol 

 penetrates quickly, but the staining after it is not entirely 

 satisfactory. 



Staining. Picrocarmine as given above for the spinal cord is 

 for general purposes the most useful stain. A -25 p.c. aqueous 



162 



