28 Neurological Technique 



13. Sections 10 micra in thickness afford the best pictures. 

 Arrange the block of paraffin and the microtome knife as directed 

 in I, 5, and make serial sections, transverse in case of spinal cord 

 or vertical in case of the cerebral cortex. Save the first sections 

 from the block. Quite often these are better than those from 

 farther in the piece of tissue from the fact of having been 

 exposed to the more immediate and perfect action of the fluids. 



14. Fasten the sections on the slidfe by the "dry method": 

 Rub a very thin film of Meyer's albumen fixative (I , F, p. 

 15) on the slide, lay the sections in position, brush them out flat 

 with a camel's hair brush, and press them down firmly with a 

 clean finger. The use of water for straightening them out, as in 

 I, 6, impairs the staining properties of the sections. 



Prepare several slides with a number of sections on each. 



15. To stain and differentiate. — {a) Remove the paraffin from 

 the sections by immersing the slide in xylol for 10 minutes. 



(^) Transfer to absolute alcohol for about 10 minutes, and then 

 pass rapidly through the decreasing grades of alcohol (I, H, 

 p. 16), 1-2 minutes in each, down to distilled water, in which it 

 should remain about 2 minutes, or only long enough to remove 

 the alcohol. 



(c) Remove the slide from the water and dry its edges and 

 under side with a cloth. Lay it level, preferably across the 

 edges of a small, thin-walled stender dish, and with a pipette 

 carefully run a layer of distilled water over the sections. The 

 dry edges permit a film of water 1-2 mm. thick. Then the 

 slide with the water on it is placed immediately in a thermostat 

 or stove, previously raised to a temperature of 55 or 60° C, for 

 3-10 minutes. 



The optimum time in the thermostat varies for different 

 pieces of tissue, and must be determined by experiment. 

 Usually 6-8 minutes produces good results. The warm water is 

 thought to remove the excess of molybdate compounds, and 

 too much may be eixtracted. 



[d) To stain, pour off the warm water, rinse by merely dip- 

 ping the slide two or three times through fresh distilled water, 



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