NEUROFIBRILS 479 



Formula 1, A. As the last, but pieces are fixed in 3 to 6 per 

 cent, silver nitrate. This formula gives better fixation, and was 

 successfully used by Dogiel {Anat. Auz., xxv, 1904, p. 558, and 

 Arch. mikr. Anat., Ixvii, 1906, p. 638) for the study of Grandry's 

 corpuscles and other sensory nerve-endings, by Kolmer {Anat. 

 Anz., xxvi, 1905, p. 560) for the epidermis of Lumbricus, etc., 

 and by other authors for the ganglionic chain of Hirudinca. 



Formula 1, B. As above, but taking 0-75 per cent, silver nitrate 

 and very small pieces, preferably from embryos and new-born 

 subjects. Poor fixation, much shrinkage, but vigorous stain of 

 the neurofibrils, nucleolar granules and the intranuclear rodlet of 

 Roncoroni. 



Formula 1, C. As above, but tissues are fixed in 2 per cent, 

 silver nitrate to which one-fourth of absolute alcohol or acetone 

 has been added. Better fixation than with pure silver nitrate. 

 Results very similar to those obtainable by Formula 1 with dog, 

 cat and rabbit, and better results with human cerebrum and 

 cerebellum. 



Formula 2. Fixation for twenty-four hours in 96 per cent, 

 alcohol. Tissues not washed, but mopped with blotting paper 

 and put into 1-5 per cent, silver nitrate for seven days at 35° C, 

 or six days at 40° C. The rest as Formula 1. Good impregna- 

 tions of nerve-centres of adults, of peripheral nerve-endings, of 

 regenerating nerves, of nerve-cells of early embryos, and of young 

 fishes. It impregnates medullated and many non-medullated 

 fibres, large and medium nerve-cells, the basket fibres of Purkinje's 

 cells, etc. 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 Cajal calls accelerators. Such are chloral hydrate, veronal, 

 pyridine, nicotine, ethylamine, antipyrine, and others. 



Hypnotics, particularly veronal and chloral, and in a less 

 degree pyridine and ammonia, also act as rejuvenators, reviving 

 the susceptibility of impregnation in tissues which have lain too 

 long in alcohol. 



Formula 2, A. Fixation for twenty-four to forty-eight hours 

 in 96 per cent, alcohol with 2 per cent, of chloral hydrate. Silver 

 bath of 1-5 per cent, for five days in the stove. The rest as usual. 

 Veronal (same proportion) gives the same residt, as do also 

 sulphonal, trional, hedonal, etc. The results are very constant. 

 Medullated fibres well shown. 



Formula 2, B. Fix for twenty-four hours in 96 per cent, 

 alcohol with 10 to 20 per cent, of pyridine ; wash for some hours 

 in pure alcohol and transfer pieces into 1-5 silver nitrate for five 

 days at 37° C. 



This formula may be successfully employed for the study of 



