424 NERVOUS SYSTEM SPECIAL METHODS. 



1-5 per cent, silver nitrate, and reduce as usual. Kesults very 

 constant, without shrinkage. Good for the fine plexuses of cere- 

 brum, bulb and cord, the baskets of Purkinje's cells, and moss 

 fibres ; also for motor plates and for regenerating nerves. 



Formula 6a, A. Fix for twenty-four hours in 10 per cent, chloral 

 hydrate, wash for six, and put direct into the silver. Stove for four 

 days. Kesults similar to those of Formula la. Medullated fibres 

 well stained. 



Formula 7a. Fix for twenty-four hours in Merck's fibrolysine, 

 wash for six, put for twenty-four into 50 c.c. of alcohol with 5 drops 

 of ammonia. The rest as by other formulae. 



Instead of fibrolysin, lysidme may be taken. 



838. Application of CAJAL'S Methods to different Objects. (1) For 



the study of the evolution of neuroblasts and nerve fibres in very 

 early embryos it is necessary to avoid fixing with formol, or alcohol 

 with an accelerator, or ammoniacal liquids. The best formulae are 

 2a and 5a which are applicable to all vertebrates, but preferably 

 to embryos of birds and fishes. 



(2) For late embryos and fatus of mammals. Besides the above 

 formulae, 3a, 6a and alcohol with an accelerator. Best subjects, 

 embryos of chick from the fifth day, and of rabbit from the tenth 

 to the twelfth day ; or new-born birds, with ammoniacal alcohol, 



or 5a. 



(3) For sympathetic ganglia. Formula 3a, or pure alcohol, or 

 4a and 5a. Best with man. Dog, cat, and rabbit give mostly 

 weak reactions. The visceral ganglia are the most difficult. 



(4) Sensory ganglia. Formula 2a or 3a. Easy. 



(5) Cerebellum. For Purkinje cells, la or 3a. For the baskets, 

 climbing fibres, and medium and small dendrites, 2a or its variants. 

 For terminal rosettes and collaterals of moss fibres and for the 

 plexuses of the granular layer, 4a or sometimes 5a or 6a. For the 

 stellate cells of the molecular layer, 2a and 3a. The best subject 

 for the latter is the dog. 



(6) Cerebrum. In general, the same formulae as for the cere- 

 bellum, especially la for pyramids of young dogs and cats (of eight 

 to twenty days). In Formula 3a the proportion of ammonia should 

 be diminished. For fine plexuses, 4a, 5a, and 6a. 



(7) Spinal cord and bulb. All the formulae are applicable. For 

 neurofibrils of motor cells the best subject is the dog of four to fifteen 

 days, with Formula 3a, with a large dose of ammonia (10 drops) ; 

 also the alcoholic fixatives with an accelerator. For medullated 



