MOUNTING IN GLYCERINE JELLY. 31 



placed over it. It is advisable first to warm the cover-glass a 

 little, as otherwise air-bubbles will easily remain in the prepara- 

 tion, and for similar reasons it is desirable not to place the cover- 

 glass on quite flatly, but with a slight lateral movement. If, in 

 spite of this, air-bubbles are enclosed, the glass-slide can be 

 warmed a little, and by careful raising of the cover-glass en- 

 deavour to bring the air-bubbles to one side. If the air-bubbles 

 are not so placed as to interfere with the sections, removing them 

 is not essential. If several sections are placed in the same drop 

 they should be dispersed in it. No doubt it will often happen 

 that, in laying the cover-glass upon them, the sections come into 

 contact with or even overlie one another, and then if the cover- 

 glass is raised on one side to secure order, a contrary result is 

 often produced. Another comparatively simple method is there- 

 fore employed. By warming the glass-slide, make the drop as 

 fluid as possible, and then, without lifting the cover-glass, pass 

 in a hair from one side, and with this hair seek out the section 

 to be adjusted, an operation which is usually successful. Before 

 covering with the cover-glass it is, above all, necessary to make 

 sure with the aid of a lens that no particles whatever of dust 

 have found access to the drop of glycerine-jelly ; any such should 

 be removed with a needle. If in the process of these various 

 manipulations the jelly has become too viscid, it can be again 

 liquified by warming. 



Preparations in glycerine-jelly do not require any " sealing, " 

 and provide, therefore, the simplest form of permanent prepara- 

 tion ; and as most vegetable objects, even when stained, keep 

 very well in it, while their structural characters even become 

 often clearer, we can recommend this method of embedding in 

 preference to all others. One or two precautions it is worth 

 while, however, to bear in mind. Very watery preparations are 

 best soaked in glycerine before placing in glycerine-jelly, or they 

 may not preserve properly ; or, if they are liable to collapse with 

 this treatment, they can be first placed in very dilute glycerine, 

 such as one part to nine of water, protected from dust, and the 

 glycerine allowed slowly to concentrate, when the prepara- 

 tion can be transferred to the jelly. Further, as the jelly 

 shrinks somewhat, after closing, and does this very slowly, it is 

 well after the lapse of some months to surround the edges of the 

 cover-glass with a narrow band of gold size, or other sealing 

 material. 



