DRY PREPARATIONS. 393 



dry very transparent and of a light colour, — should be injected with 

 vermilion, if we use red, for vermilion is the lightest red of any that 

 can be called a good red ; therefore it makes a greater contrast between 

 the vessels and the thing itself. But the kind of injection will make a 

 good deal of difference in the colour, for all reds become much deeper 

 by being mixed with oily substances, therefore the colour that is fit for 

 oil, is much too pale when mixed with water and spirits, and vice versa. 



Many parts of fishes that are intended for dry preparations should 

 first be steeped in spirit ; this coagulates all their juices, preserves them 

 from putrefaction, and allows of a quicker evaporation, all of which 

 are often absolutely necessary. 



Of Varnishing. — Varnishing dry preparations has three advantages ; 

 first, it prevents their being destroyed by insects ; secondly, it preserves 

 them from the dirt, as any dirt will easier come off a smooth coat of 

 varnish than off the preparation itself ; and thirdly, it gives the prepa- 

 ration a much brighter colour, and makes the part shine by entering its 

 pores, thereby rendering it more transparent. The varnish being a 

 transparent body itself, and entering the pores, fills them up : thereby 

 the whole becomes a more uniform mass, having fewer reflecting sur- 

 faces, and therefore the deeper-seated parts that are bright (viz. the 

 injected vessels) are better seen. Varnishing preparations is as neces- 

 sary a part as any, as it keeps them clean and free from insects ; and 

 for this last purpose it is necessary to be extremely nice : the parts that 

 -are easiest varnished are those which have least occasion for it, it being 

 the hollow corners or crevices that require it most, as it is there the 

 insects lay their eggs, the worms from which destroy the preparation. 

 Insects often eat their way through the varnish into the preparation ; to 

 prevent which, dissolve corrosive sublimate in spirit of wine, and mix 

 it with the varnish before it is laid on the preparation. 



The spirit varnish is most proper for those preparations that are to be 

 handled, because the gum that dissolves in spirit does not in water ; so 

 that the moisture of the hand does not soil it. It likewise does best for 

 those preparations that have any grease in them; for it in some 

 measure mixes with the grease, and therefore adheres more firmly to 

 the preparation ; whereas the watery gum does not, so that it rises in 

 blisters. 



Spirit varnish is best for corroded preparations ; it is better than the 

 copal, because it does not dissolve any of the injection on the surface, 

 which is the case with the copal, and all the turpentine varnishes ; and 

 when they dissolve the wax on the surface of the smaller vessels, it al- 

 most goes through and through, by which means they bend or collapse. 



Mr. Henry's copal varnish dries very readily, but when perfectly dry 



