12 Neurological Technique 



the shortest time mentioned is, in all cases, the minimal, for 

 pieces of tissue of the size suggested. In fixing especially, quite 

 an amount of latitude is often allowable, the tissue not being 

 injured by remaining in some of the fixing fluids several hours, or 

 sometimes days, after the fixation is complete. Likewise in 70 

 or 80 per cent, alcohol, usually the tissue and sometimes the 

 unstained sections may remain indefinitely. 



5. The forms in which the formulae are given are those 

 which are considered most easy to follow in the making up, and 

 at the same time the resulting fluids will, in most cases, be in 

 sufficient quantity to apply the method to such an amount of 

 tissue as is ordinarily needed. 



6. The word "replace" is used in the directions when it is 

 thought more expedient to pour off ox remove the fluid in which 

 the tissue then is, and pour on the fluid required. The word 

 " transfer," on the other hand, indicates to remove the mate- 

 rial or slide from one fluid and place it into another. 



7. The graded alcohols will be necessary in most of the 

 methods, and would best be made in quantity and kept on hand. 

 For preparing them see formula and table, p. 10. 



8. Slides and cover-glasses should always be thoroughly 

 cleaned. This is especially necessary for parafifin sections. 

 Sections cannot be fastened permanently to a soiled or oily slide. 

 New slides need cleaning as well as old ones. 



The following slide-cleaning fluid may be used with excellent 



results : 



Potassium bichromate, 25 g. 

 Sulphuric acid, 25 cc. 

 Distilled water, 200 cc. 

 First dissolve the bichromate in the water and then add the acid. 



This fluid used in sufficient quantity will also clean slides 

 which have been used for balsam mounts. Warm till the old 

 balsam is softened, remove the cover, scrape off most of the 

 balsam from the slide with a knife, and place both slide and 

 cover into the fluid. After a day or so they may be simply 

 washed well in distilled water and wiped dry with a clean cloth. 



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