72 Neurological Technique 



7. To counterstain. — The nerve-cell bodies and all the con- 

 nective tissue elements are usually completly decolorized. 

 Their position, however, may be seen without further treatment. 

 If it is desired to bring out the cell-bodies more clearly, the sec- 

 tions may be transferred from the water to a small amount of 

 Upson's carmine' for 5-10 minutes. If the object is to study 

 the medullated fiber-tracts, it is best not to counterstain at all. 

 For the study of developing meduUation or degenerated fiber- 

 tracts, the more nearly colorless the background is in which the 

 steel-blue fibers are situated, the better. 



8. After counterstaining or omitting the same, the sections 

 are to be dehydrated, cleared, and mounted as in X, 10, p. 66. 



SERIAL SECTIONS. 



Before staining, the sections cannot be fastened to the slide 

 serially, since each section must be differentiated individually and 

 also since the differentiation takes place evenly only when the 

 section is free, so that the differentiating fluids may act upon it 

 equally from both sides. 



When serial sections are desired, the following simple device 

 may be employed: Prepare 12 or 15 shallow dishes with covers 

 and number them in series. As the sections are cut, place them 

 in the dishes in the order in which they come from the knife. 

 Usually, in an organ or structure from which serial sections are 

 necessary, each twelfth or fifteenth section will show some vari- 

 ation by which, it may be distinguished. If not, then after each 

 set of fifteen sections trim or notch the celloidin block in such 

 a way that the sections belonging to the next set can be distin- 

 guished by the contour of the celloidin about them. Make a 

 note of the characteristic marking of each set in the order in 

 which it is made. Thus the fifteen dishes will contain the sections 

 in series, each dish containing sections taken at intervals of 

 fifteen. 



Then stain, differentiate, dehydrate, and clear each dish of 



' Upson's carmine: — Boil S grams of ammonia alum and i gram of powdered car- 

 mine in 100 cc. of distilled water for 10-20 minutes. When cool, filter and to each 

 50 cc. add 2 cc. of a 10 percent, aqueous solution of phosphomolybdic acid. 



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