480 NEUROFIBRILS 



peripheral nerve-endings. In this case material is better fixed 

 for twenty -four hours in pyridin to which one-third its volume 

 of distilled water or 96 per cent, alcohol has been added. Pieces 

 should be washed in running tap-water overnight and then 

 transferred for six hours into pure 96 per cent, alcohol. Impreg- 

 nation, reduction, imbedding, etc., as above. Results are good, 

 but pieces become extremely hard even if dehydrated very 

 quickly, and are consequently difficult to cut. See also Formula 5. 



Formula 2, C. Fix for twenty-four hours in 50 c.c. of alcohol 

 with 10 drops of nicotine. Mop up with blotting paper, without 

 washing, and silver as usual for five days (or four at 40° C). 

 Good results with adult tissues, especially spinal cord. Good 

 penetration and less shrinkage than with pure alcohol. 



Formula 2, D. Fix for twenty-four hours in allylalcohol (the 

 industrial product will do). Wash for some hours in several 

 changes of water. Put for a day into 50 c.c. of alcohol with 

 4 drops of ammonia. Silver for four days at 35° to 38° C, and 

 reduce as usual. Good for human tissues, especially for fibre 

 plexuses of cerebrum and cerebellum. Instead of allylalcohol 

 one may take acetal or acetone. Put for six hours into acetone 

 with 25 per cent, of water, then for twenty-four into pure acetone, 

 wash in water, etc., as above, 



Forynula 3. Fixation in ammoniacal alcohol for twenty to 

 forty-eight hours. The most generally useful formula is 50 c.c. 

 of 96 per cent, alcohol with 4 to 5 drops of ammonia (of 22° 

 strength). But for cerebrum not more than 1 to 3 drops ; for 

 cerebellum, ganglia, spinal cord and regenerating tracts, 4 drops ; 

 for neurofibrils of the large nerve-cells of the medulla oblongata 

 and spinal cord, 9 to 10 drops. To avoid shrinkage, it is well to 

 begin by putting the pieces for six hours into 70 per cent, alcohol, 

 then in 85 per cent., without ammonia ; then for the rest of the 

 time into the ammoniacal alcohol. Do not wash, but mop up 

 with blotting paper before putting into the silver. Silver for 

 four to four and a half days (small specimens) at 40° C, or medium 

 to large (3 to 4 mm. thick) for five days at 32° to 35° C. So 

 long as the tissues are only yellowish-white, they are not ripe for 

 reduction ; light grey indicates ripeness ; dark grey over-ripeness. 

 Reduce as by Formula 1. 



Specimens may be decalcified, after reducing and washing, in 

 96 per cent, alcohol to which a few drops of nitric acid have been 

 added. 



For the impregnation of the neurofibrils of large and medium 

 nerve-cells this formula is superior to all others. It gives good 

 results with the majority of nerve-centres, and is particularly 

 good for non-medullated fibres, peri-cellular baskets of cere- 

 bellum, buds of Held and Auerbach in the oblongata, spinal and 

 sympathetic ganglia and regenerating nerve-fibres. 



