xlviii INTRODUCTION. 



METHODS OF MOUNTING SECTIONS. 



MOST sections, even when very thin, are too opaque to be examined, and must therefore be 

 placed in some medium or mounting fluid which will render them more transparent. 



MOUNTING FLUIDS. 



1. Glycerine. The section must be floated on to a slide from water, and, after removing 

 the water, a small drop of glycerine is applied. The drop ought to be of just such a size 

 that when the cover-glass is applied, it accurately fills the space between the cover and the 

 slide. Apply a cover-glass, as directed (p. xxiv). A little practice is required to gauge 

 the size of the drop required. If too much glycerine be added, the excess is most conveniently 

 removed by placing several small pointed pieces of bibulous paper round the margin of the 

 cover. All surplus glycerine must be carefully removed, else the cement to be afterwards 

 applied will not adhere to the glass. Glycerine has this great disadvantage, that the cover- 

 glass moves so easily that it becomes difficult to seal up the preparation. This is entirely obviated 

 by mounting sections in the following fluid, which has the advantage, that after exposure to the 

 air for three or four days, the cover-glass becomes firmly fixed to the slide, so that the coat- 

 ing of cement can be applied without any fear of .displacing either the cover or the section. 



2. Farrants Solution. Take equal parts of glycerine and a saturated watery solution of 

 arsenious acid. Add gum arabic in large quantity, and allow the mixture to stand for several 

 weeks, stirring it from time to time, until it ceases to dissolve more of the gum. Filter through 

 paper. This takes a considerable time, but one is rewarded by the beautifully clear fluid 

 obtained. 



The above fluids are suitable for mounting sections stained or unstained from water. 

 Unless for very delicate tissues, such as isolated epithelial cells, Farrant's solution is in all 

 cases to be preferred. It is always advisable, when wishing to study the minute relations of 

 parts except those of the nerve-centresto mount sections in either of the above fluids. 



3. Glycerine Jelly. This is sometimes employed to mount softened bone and tooth, and 

 some urinary deposits. It must be melted in a water bath before being used. As it sets rapidly, 

 the cover-glass must be applied at once to the preparation. It is far better to buy it ready- 

 made than to take the trouble of making it. Rimington's is the best : it contains, in addition 

 to gelatine and glycerine, a trace of carbolic acid. 



4. Dammar Solution. Mix in an earthenware vessel 2 oz. of mastic and 2 oz. of dammar with 

 2 oz. of chloroform and 2 oz. of turpentine. Shake or stir the mixture from time to time until the 

 substances are dissolved. Filter through paper. Formerly Canada balsam was employed, but 

 the above fluid is certainly to be preferred. If Canada balsam be thought preferable, it may be 

 easily prepared by heating some balsam in a capsule in a warm chamber at 65 C. for twenty- 

 four hours, and, after it cools, dissolving the dry yellow mass in as much benzole as will give a 

 fluid of a syrupy consistence. 



