154 PRACTICAL HISTOLOGY. 



for the salivary glands and pancreas. While hardening 

 albuminous tissues it removes calcareous matter ; on this 

 account it is useful in the preparation of bone ( 119). It 

 gives the tissues a deep yellow tinge, which may, however, 

 be removed by immersion in water or in alcohol. In the 

 case of chromic acid the colour is much more difficult to 

 remove. 



276. Miiller's Fluid is thus prepared : 



Potassium bichromate, 2*5 grammes. 



Sodium sulphate, i gramme. 



Distilled water, icoCC. 



This fluid is very useful for hardening the liver, kidney, 

 ovary, etc. (pp. 4 and 5). It is sometimes termed Miiller's 

 eye fluid, on account of its having been originally employed 

 for hardening the retina. For this purpose, however, it is 

 inferior to a mixture of chromic acid and alcohol. After 

 the use of Miiller's fluid for a month or so, the hardening 

 is carried still farther by the employment of rectified spirit. 



277. Potassium Bichromate is the hardening agent 

 in Miiller's fluid. This substance may, however, be employed 

 alone. A i or 2 per cent solution in water is useful for 

 hardening glands; from two weeks to a month are required. 

 Hardening is carried still farther by immersion in rectified 

 spirit, which also removes much of the colour. 



278. Alcohol is useful when rapid hardening is re- 

 quired. It acts by removing water and coagulating 

 albumin. It is one of the oldest of indurating agents. It 

 is specially useful for yellow fibro-cartilage ( 114) and 

 gland tissues. The ordinary rectified spirit (sp. gr. 0-838), 

 and absolute alcohol are the best forms. Methylated spirit, 

 often recommended, is to be avoided. The tissues should 

 be placed first in equal parts of rectified spirit and water 

 for a day ; then in rectified spirit for forty-eight hours, and 

 finally in absolute alcohol for some hours, to complete the 

 hardening. The tissues spoil if they are allowed to remain 

 too long in the alcohol, unless they have been previously 

 hardened in chromic, picric, or osmic acids, or potassium 

 bichromate and such like. Alcohol is now rarely employed 

 alone, but it is very useful for completing the hardening of 



