46 Neurological Technique 



teased preparations. For a more detailed study of the intimate 

 nature of these relations, sections are required. Directions for 

 sections will be given below. 



BY IMMERSION. 



Material difificult to inject, or such as failed to take the 

 stain after injection, may be stained by a local application of the 

 stain. 



Make a o.i per cent, solution of the methylenrblue by dilut- 

 ing 10 volumes of the i per cent, solution (B) with go volumes 

 of the physiological salt solution (A.) 



From a freshly killed animal remove small pieces of the 

 tissue required and place on a slide or in a shallow watch-glass 

 wet with physiological salt solution. Gently divide into smaller 

 pieces of suitable size (2—3 mm. thick), and add a few drops of 

 the 0.1 per cent, solution of the stain. At intervals of about 5 

 minutes add a fresh drop of the diluted stain, always keeping 

 the tissue well moistened by the solution, but never covered by 

 it. The pieces are thus exposed to the action of the stain and to 

 the air at the same time. 



Examine the pieces from time to time under the micro- 

 scope without covering them. The length of time in which the 

 nerve elements become satisfactorily stained by this method 

 varies. It usually takes from one-half hour to one hour, but it 

 may take much longer. 



When examination shows that the elements are well stained, 

 fix in the ammonium picrate solution as directed above (4), and 

 preserve and mount in the ammonium picrate-glycerine mixture 

 as directed in step 5. 



FROZEN SECTIONS. 



When the necessary teasing would too much distort the 

 arrangement of the nerve elements, or when it is especially 

 desired to study a structure in situ, frozen sections are some- 

 times employed. Frozen sections, however, are liable to stain 

 diffusely, and indeed seldom, if ever, give the distinct pictures 

 obtained by the injection of the stain directly into the fresh 

 tissues. 



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