AXIS-OYLINDER AND DENDRITE STAINS. 421 



of Invertebrates — Insects, Lumhricus, Tuhifex, Helix, Limax, 

 Distomum, Astacus, Actinida, etc. 



The method has been desci'Ibed at length by Golgi in the 

 Archives Italiennes de Biologie, t. iv, 1888, p. 32 eb seq., and 

 vii, 1886, p. 15 et seq. The following account is from the 

 latter paper. The earlier form of the method should not be 

 followed. 



810. GoLQi'.s Bichromate and Nitrate of Silver Method, SLOW 

 Process [loc. cit., p. 17). — (a) The hardening. — The tissues 

 must be hardened in a bichromate solution. Either pure 

 bichromate of potash may be employed, or liquid of Miiller 

 (the reaction can be obtained with liquid of Erlicki, but it is 

 not to be recommended). The normal practice is to take 

 bichromate of potash, beginning with a strength of 2 per 

 cent., and changing this frequently for fresh solutions of 

 gradually increased strength, 2^, 3, 4, and 5 per cent. The 

 tissue should be as fresh as possible ; though satisfactory 

 results may sometimes be obtained from material taken 

 twenty-four to forty-eight hours after death.* It should he 

 in pieces of not more than 1 c.cm. or l^ c.cm. in size. 



The most difficult point of the method consists in hitting 

 off the exact degree of hardening in the bichromate that 

 should be allowed before passing to the next stage. In 

 summer good i-esults may be obtained after fifteen to twenty 

 days, and the material may continue in a favourable state for 

 impregnation up to thirty, forty, or fifty days. In cold 

 weather good results can seldom be obtained under a month : 

 when obtained, the material may continue to give good results 

 up to two, three, and even four months of hardening. The 

 only way to make sure is to pass trial portions of the tissue 

 at intervals into the silver-bath, in summer frequently, in 

 winter every eight or ten days, and observe whether the 

 reaction is obtained. 



Good results are obtained by injecting the organs with 

 the hardening fluid (2'5 per cent, bichromate). See § 737. 



Stoving at a temperature of 20 to 25 0. is useful for 



* Material that has been hardened in formol may also be used. See 

 § 817 (Gbeota and Bolton), and v. Lenhossek's Feinere Bern d. 

 Nei-iensy stems, p. 23. I Lave had good results with material that had 

 been three months in formol (I have not tried older). 



