394 CHAPTER XXXII. 



Formula 2a D. — Fix for 24 hours in rilli/l alcohul (tlie 

 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 4 days at 

 35° to 38° C, and reduce as usual. Good for human tissues, 

 especially fibre plexuses of cerebrum and cerebellum. 

 Instead of allyl alcohol you may take acetal or aceton. Put 

 for six hours into aceton with 25 per cent, of water, then for 

 24 into pure aceton. 



Formula 3a. — Fixation in nmmoniacal oJcohol for 20 to 48 

 houi's. The most generally useful formula is, 50 c c. of 

 alcohol of 96 per cent, with four to five drops of ammonia 

 (of 22° strength). But for cerebrum not more than one to 

 three drops : for cerebellum, ganglia, spinal cord and 

 regenerating tracts, four drops : for neurofibrils of the large 

 neurons of the bulb and cord, nine to ten drops. To avoid 

 shrinkage, it is well to begin by putting for six hours into 

 alcohol of 70 per cent., then 85 per cent, without ammonia, 

 then for the rest of the time into the ammoniacal alcohol. 

 Do not ivaah, 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 5 days at 32° to 35° 0. 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 

 formula la. 



Specimens may be decalcified, after reducing and washing, 

 conveniently in alcohol of 96 per cent, with a few drops of 

 nitric acid. 



For delicate impregnation of fibrils of the soma of large 

 and medium neurones, this formula is superior to all others. 

 It gives good results with the majority of nerve centres, and 

 is ])articu]arly good for non-medullated fibres, peri-cellular 

 baskets of cerebellum, buds of Held and Auerbach in the 

 oblongata, for human sympathetic, and for the study of 

 regenerating elements. 



Formula 3a A.— Fix in 50 c.c. of alcohol with 10 grm. of 

 glycerin and six to ten drops of ammonia. Good for retina, 

 non-medullated fibres, and especially the buds of Held and 

 Auerbach. 



Formula 3a B— Fix in 50 c.c. of alcohol with 1-5 c.c. of 



