NI5BV0US SYSTEM — OYTOLOGtOAL METHODS. 393 



Formula la* Good impregnations of nerve-centres of adults, 

 of peripheral nerve-endings, of regenerating nerves, and of 

 early embryos and of young fishes. Impregnates meduUated 

 (and many non-medullated) fibres (black), large and medium 

 neurones (fibrils browji), the basket fibres of cells of 

 Purkinje, the granular layer, and in the cerebrum large and 

 medium pyramidal cells and nerve-fibres. Results fairly 

 constant, but sometimes showing a granular precipitate of 

 unknown origin. 



To hinder this precipitate, and at the same time to hasten 

 the impregnation, it is well to add to the alcohol certain 

 substances which Ramon calls " accelerators.'" Such are 

 chloral hj'drate, veronal, pyridin, nicotin, ethylamin, anti- 

 pyrin, and others. 



Hypnotics, particularly veronal and chloral, and in a less 

 degree pyridin and ammonia, also act as rejuvenators, reviving 

 the susceptibility of impregnation which has been lost by 

 tissues that have lain too long in alcohol. Ramon has thus 

 succeeded with pieces of cerebrum and cerebellum that had 

 been half a year in alcohol. 



Formula 2a A. — Fixation for 24 to 48 hours in alcohol 

 of 9(J per cent, with 2 per cent, of hydrate of chloral added. 

 Silver bath of 1'5 per cent, for five days in the stove. The 

 rest as usual. Veronal (same proportion) gives the same 

 result, as do also sxil^ihonul, trional, hedonal, etc. The results 

 are very constant. MeduUated fibres well shown. 



Formula 2a B. — Fix (time not stated) in alcohol with 10 to 

 20 per cent, of pyridin, wash for some hours in pure alcohol, 

 and silver as usual (5 days). Results regular and constant. 



Formula 2a C. — Fix for 2-1 hours in 50 c.c. of alcohol 

 with ten drops of nicotin. Mop up with blotting paper, 

 without washing, and silver as usual for five days (or four at 

 40° C). Grood results with adult tissues, especially spinal 

 cord. Good penetration and less shrinkage than with pure 

 alcohol. 



* If the impregnation of inner layers should be too weak, the sections 

 may be toned with — • 



Water 100 c.c. 



Sulphocyanide of ammonium 3 gr. 



Hyposulphite of sodium 3 ,, 



1 per cent, gold chloride , , a few drops. 



