48 Neurological Technique 



hours the fluid with the tissue in it must be kept on ice. During 

 the rest of the period of fixation the fixative may be allowed to 

 assume the ordinary room temperature without injury. 



3. After fixation, the tissues must be washed in distilled water 

 for i-i J^ hours to remove the surplus molybdate, which other- 

 wise will produce crystals in the preparations. 



4. To harden and dehydrate, the pieces are transferred from 

 the water directly to absolute alcohol. It is necessary to hasten 

 the dehydration as much as possible without endangering its 

 completeness. To do this use 3 or 4 changes of absolute 

 alcohol, 20-30 volumes at a time, and agitate the alcohol about 

 the specimens from time to time. Pieces of tissue of 3-4 milli- 

 meters' thickness should become dehydrated in about i hour. 



5. Clear in 10-15 volumes of xylol for i-ij^ hours. 



6. Imbed in parafiSn and cool parafifin block as in I, 4, {a) to 

 {d), p. 16. 



7. Make sections of the thickness desired (see I, 5, p. 17). 



8. Fasten sections to the slide by either the " albumen water 

 method" (I, 6, p. 17) or by the "dry method" (III, 14, p. 28). 



9. Dissolve off parafifin in xylol (I, 7, p. 18) and mount 

 directly in balsam (I, 16, p. 19), or, if desired, the sections 

 may be counterstained in alum-carmine or alum-cochineal. To 

 do this transfer from xylol to absolute alcohol for 5-10 minutes; 

 then pass successively through 95 per cent., 70 per cent., and 

 50 per cent., about i minute in each. Transfer from 50 per 

 cent, alcohol to the stain for about J^ hour. 



Wash off stain in 50 per cent, alcohol and dehydrate by pass- 

 ing up through the grades of alcohol, 70 per cent, i minute, 95 

 per cent. 2 minutes, absolute alcohol 10 minutes. Clear in oil 

 of bergamot or pure xylol for 10 or 15 minutes and mount in 

 balsam as before. If oil of bergamot is used, and it is better 

 for the clearing, rinse off the surplus oil in pUre xylol before 

 mounting. 



Bethe ' has recommended a procedure by which the neces- 



' A. Bethe, " Eine neue Methode der Methylenblaufixation," Anatomische Anzei- 

 ger, Bd. XII, p. 438, 1896. 



Digitized by Microsoft® 



