42 FIXING AND HARDENING AGENTS. 



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

 alcohols of increasing strength, beginning with 15 per cent. 



Mixtures of bichromate with osmic acid have been given above, 42, 



43 and 44. 



53. MULLER'S Solution.- 



Bichromate of potash . . . 2 2J 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. 



54. ERLICKI'S Solution (Warscliauer med. Zeit., xxii, Nos. 15 and 

 18 ; Progres Medical, 1897, No. 31) : 



Bichromate of potash . . . 2-5 parts. 



Sulphate of copper .... 1-0 part. 



Water ...... 100-0 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 

 bichromate or Miiller's solution. A spinal cord may be hardened 

 in it in four days at the temperature of an incubator, 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 Eiiicki'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. wiss. 

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

 annee, i, p. 20). 



55. KULTSCHITZKY'S Solution (Zeit. wiss. Mik., iv, 1887, p. 348). A 

 saturated solution of bichromate of potash and sulphate of copper in 

 50 per cent, alcohol, to which is added at the instant of using a little 

 acetic acid, 5 or 6 drops per 100 c.c. 



To make the solution, add the finely powdered salts to the alcohol in 



