22 Neurological Technique 



cube usually become cleared, i. e., penetrated thoroughly by the 

 oil, and ready for the paraffin in 30-40 minutes. 

 Xylol may be used alone (see I, 3, note, p. 16). 



4. Imbed in paraffin, make sections 4-6/* thick, fasten 

 sections on the slide, and dry as directed in I, 4, 5, and 6, p. 16. 



5. To stain. — {a) When dry, dissolve off paraffin in xylol, 

 10-20 minutes, and then transfer slide from xylol to absolute 

 alcohol for 5-10 minutes (see I, 7 and 8, p. 18). 



Note. — The stain to be used in this case is a water solution. Should the 

 sections be passed from a high grade of alcohol to a much lower one, or 

 directly to water, the resulting diffusion currents would endanger a breaking 

 up of the cell contents. For this reason it is necessary to pass the slide suc- 

 cessively through the grades of alcohol of diminishing strength. Use slide 

 jars or wide-mouthed bottles. 



{b) Transfer slide from absolute to 95 per cent, alcohol, 5 

 minutes. From 95 per cent, transfer to 70 per cent, alcohol, 5 

 minutes. From 70 per cent, transfer to 50 per cent, alcohol till 

 stain is ready. 



(r) In a test-tube, heat about 10 cc. of the stain (B) till it 

 steams. 



[d] Lay the slide level and pour enough of the warm stain 

 over the sections to cover them well. Let the stain act 4-6 

 minutes. 



6. To differentiate. — («) Drain the slide and quickly rinse off 

 the surplus stain by gently running distilled water over it. 



(b') Wipe the back and edges of the slide dry, again lay it 

 level, and flood with the aniline-alcohol mixture (C). 



(c) Let this decolorize till the sections become a pale blue 

 with a slight rose tint, i. e., nearly colorless. This usually occurs 

 in 'from 20 to 30 seconds. During this period the sections may 

 be observed more closely if the aniline alcohol is changed after 

 the first few seconds. 



7. To clear, quickly drain and wipe off the aniline-alcohol from 

 the free surfaces of the slide, lay it level sections uppermost, 

 and flood with oil of cajeput (D, 2). When no cloudiness is seen 

 on viewing the sections over a dark surface, the sections are 

 cleared. It may be necessary to renew the oil. 



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