STAINING PROCESS. 189 



allowed to cool. After the lapse of an hour, much of the excess 

 of ammonia will have escaped ; and the solution is then to be 

 mixed with 2 oz. of Distilled Water, 2 oz. of pure Glycerine, and 

 \ oz. of Alcohol. The whole may he passed through a filter ; or, 

 after being allowed to stand for some time, the perfectly clear 

 supernatant fluid may be poured off and kept for use. If, after a 

 long keeping, a little of the Carmine should be deposited through 

 the escape of the ammonia, the addition of a drop or two of Liquor 

 Ammoniac will re-dissolve it. The most valuable result of this 

 process is the facility with which, when carefully and judiciously 

 employed, it enables the Microscopist to distinguish what Dr. 

 Beale terms 'germinal matter,' — which is identical with the 

 ' protoplasm ' or ' sarcode ' of other Physiologists — from the 

 ' formed materials ' or tissue-elements, which are the products of its 

 activity ; the living formative substance being stained by Carmine 

 so much sooner than any of those products, that it may be deeply 

 dyed whilst they remain colourless. "The rapidity," says Dr. 

 Beale, "with which the colouring of a tissue immersed in this 

 fluid takes place, depends partly upon the character of the tissue, 

 and partly upon the excess of ammonia present in the solution. 

 If the solution be very alkaline, the colouring will be too intense, 

 and much of the soft tissue or imperfectly developed formed mate- 

 rial around the germinal matter is destroyed by the action of the 

 alkali. If, on the other hand, the reaction of the solution be 

 neutral, the uniform staining of tissue and germinal matter may 

 result, and the appearances from which so much may be learned 

 are not always produced. "When the vessels are injected with the 

 Prussian blue fluid, the Carmine fluid requires to be sufficiently 

 alkaline to neutralize the free acid present. The permeating power 

 of the solution is easily increased by the addition of a little more 

 water and alcohol. In some cases the fluid must be diluted with 

 water, alcohol, or glycerine ; and the observer must not hastily 

 condemn the process, or conclude (as some have) that a particular 

 form of germinal matter is not to be coloured, until he has 

 given the plan a fair trial, and tried a few experiments."* Of the 

 special uses of this method, various illustrations will be given 

 hereafter. 



146. Preparation of Specimens in Viscid Media. — To Dr. 

 Beale the Microscopist is also indebted for a method of pre- 

 paring Animal and Vegetable tissues for examination under the 

 l-12th, l-20th, or l-25th-inch Objectives, which is much supe- 

 rior to those in ordinary use. This consists in the substitution of 

 a viscid medium, such as pure Glycerine or strong Syrup, for 

 the Aqueous fluids with which the object to be examined is usually 

 treated ; many advantages being thereby gained. Thus in thin- 

 ning-out tissues by compression, an amount of pressure may be 



* " How to Work with the Microscope," 4th edit. p. 109. 



