MINERAL ACIDS AND THEIR SALTS 39 



has been added 1 drop per watch-glassful of 5 per cent, solution of 

 oxalic acid. 



The simple aqueous solution of bichromate is hardly to be recom- 

 mended as a fixing agent, because not only does it not preserve nuclei 

 properly, but also because it penetrates very slowly. The first of these 

 defects may be overcome entirely, the second to some extent by addition 

 of acetic acid ; whence the liquid of Tellyesniczky, next §. 



57. Acetic Bichromate (Tellyesniczky, Arch. mik. Anat., lii, 1889, 

 p. 242) : 



Bichromate . . . . . 3 grm. 



Glacial acetic acid .... 5 c.c. 



Water 100 „ 



Smaller objects to remain in the fluid for one or two days, larger ones 

 longer. Wash well in plenty of water, and pass through alcohols of 

 increasing strengths, beginning with 15 per cent. 



Mixtures of bichromate with osmic acid have been given above, §§ 48 

 et seq. 



58. MiJLLER's Solution. 



Bichromate of potash . . . 2 — -2^ parts. 



Sulphate of soda .... 1 part. 



Water . . . . . .100 parts. 



The duration of the reaction is about the same as with the 

 simple solution of chromic salt. 



Recent authors find the action of this liquid to be identical 

 with that of plain bichromate, and doubt whether the sulphate 

 in it has any effect whatever as regards its hardening properties. 

 Fol says that for mammalian embryos, for which it has been 

 recommended, it is worthless. 



59. Erlicki's Solution {Warschauer med. Zeit., xxii, Nos. 15 and 18 ; 

 Progres Medical, 1897, No. 31) : 



Bichromate of potash . . . 2-5 parts. 



Sulphate of copper . . . . 10 part. 



Water 1000 parts. 



Here the addition of the cupric sulphate is intelligible, for this salt 

 is itself a hardening agent of some energy. As a matter of fact, 

 " Erlicki " hardens very much more rapidly than either simple bichro- 

 mate or Miiller's solution. A spinal cord may be hardened in it in 

 four days at the temperature of an incubator (30° — 40° C), and in ten 

 days at the normal temperature (Fol, Lehrb. d. vergl. mik. Anat., p. 106). 

 Human embryos of several months may be conveniently hardened in it. 



Nerve-centres that have been hardened in Erlicki's fluid frequently 

 contain dark spots with irregular prolongations, simulating ganglion- 

 cells. These are now known to consist of precipitates formed by the 

 fluid. They may be removed by washing with hot water, or with water 

 slightly acidified with hydrochloric acid, or by treating the specimens 

 with 0-5 per cent, chromic acid before putting them into alcohol 

 (TscHiscH, Virchow's Arch., Bd. xcvii, p. 173 ; Edinger, Zeit. iviss. 

 Mik., ii, p. 245 ; Loewenthal, Rev. med. de la Suisse romande, 6me 

 annee, i, p. 20). 



60. Kultschitzky's Solution (Zeit. wiss. Mik., iv, 1887, p. 348). A 

 saturated solution of bichromate of potash and sulphate of copper in 



