CHAPTER XXXII. 421 



silver nitrate. This formula gives better fixation, and was success- 

 fully used by DOGIEL (Anat. Anz., 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^^. Anz., xxvi, 1905, 

 p. 560) for the epidermis of Lumbricus, etc., and by other authors 

 for the ganglionic chain of Hirudinea. 



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

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

 j ects. Poor fixation, much shrinkage, but vigorous stain of the neuro- 

 fibrils, nucleolar granules and the intranuclear rodlet of Roncoroni. 



Formula la, 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 la with dog, cat and 

 rabbit, and better results with human cerebrum and cerebellum. 



Formula 2a. 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 la. Good impregnations of 

 nerve centres of adults, of peripheral nerve endings, of regenerating 

 nerves, 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 2a, 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 result, as do also sulphonal, 

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

 fibres well shown. 



Formula 2a, 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. 



