ERLICKI'S SOLUTION. 49 



few minutes in a 1 per cent, solution of chloral hydrate. Gierke, however, 

 sajs that this treatment is prejudicial to the preservation of the tissues. 



76. Miiller'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 salts. 



This fluid was very highly in vogue for many years, but 

 seems lately to be much less used. I fancy that the supe- 

 riority of this mixture over the simple bichromate solution 

 is not illusory, and is due to the formation in it of a trace of 

 free chromic acid. Fol says that for mammalian embryos, for 

 which it has been recommended, it is worthless. 



77. Erlicki's Solution (Warschauer med. Zeit., xxii, Nos. 15 



and 18). 



Bichromate of potash . . . 2*5 parts. 

 Sulphate of copper . . . I'O part. 

 Water . . . . . 10OO parts. 



Here the addition of the cupric sulphate is intelligible. 

 This salt is itself a hardening agent of some energy, and may 

 well serve to reinforce the somewhat slow action of the bi- 

 chromate. As a matter of fact, " Erlicki" hardens very much 

 more rapidly than either simple bichromate or Miiller's solu- 

 tion. 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). 

 I believe it to be one of the best hardening agents known for 

 voluminous objects. 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 

 were at one time taken to be pathological formations, but they are now known 

 to consist of precipitates formed by the action of the hardening 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 (TscniscH, Virchow's Arch. r 

 Bd. xcvii, p. 173 ; EDINGEE, Zeit.f. wiss. Mile., ii, 2, p. 245 ; LOEWENTHAL, 

 Rev. med. de la Suisse romande, 6me annee, i, p. 20). 



4 



