210 THE MICROSCOPE AND ITS REVELATIONS. 



( 193); and also for mounting tlio chitinous textures of Insects, which it- 

 has a peculiar power of rendering transparent, and which seem to be- 

 penetrated by it more thoroughly than they are by the artificially-prepared 

 solution ( 210). The solution of Dammar in benzole is very convenient 

 to work with, and hardens quickly. 



206. The following are the principal aqueous media whose value has 

 been best tested by general and protracted experience: 



a. Fresh specimens of minute Protophytes can often be very well preserved IEL 

 in Distilled Water saturated with Camphor; the complete exclusion of air serving 

 both to check their living actions and to prevent decomposing changes. When 

 the preservation of color is not a special object, about a tenth part of Alcohol may 

 be added, and this will be found a suitable medium for the preservation of many 

 delicate Animal textures. 



b. Aqueous Solution of Carbolic Acid. Even the very small quantity of this 

 agent which cold water will take up, has a powerful preservative effect; and the 

 solution may be advantageously employed for mounting preparations of many 

 delicate structures, both Animal and Vegetable. 



c. The same may be said of Salicylic Acid, which has been very successfully 

 employed for delicate preparations in th.3 small proportion that will dissolve in 

 cold water. For coarser structures a stronger solution is preferable; and this may 

 be made by combining with the acid a small quantity either of borax dissolved in 

 glycerine or of acetate of potass. 



d. "Where the preservation of minute histological detail is not so much desired, 

 as the exhibition of larger structural features of objects to be viewed by reflected 

 light, nothing is better than Dilute Spirit; the proportion most generally service- 

 able being 1 of Alcohol to 4 or 5 of water; and an even weaker mixture serving to 

 prevent further change in tissues already hardened by strong Alcohol. The 

 Author has a series of the beautiful Pentacrinoid larvae of Comatula (Plate xxi.) 

 thus preserved in cells twenty years ago; which are as perfect as when first 

 mounted. The,se weaker mixtures have no action on Gold-Size. 



Of late years, Glycerine has been largely used as a preservative; either 

 alone, according to the method of Dr. Beale ( 208), or diluted with 

 water, or mixed with gelatinous substances. It is much more favorable 

 to the preservation of color than most other media; and is therefore spe- 

 cially useful as a constituent of fluids used for mounting Vegetable objects 

 in their natural aspects. It has also the property of increasing the trans- 

 parence of Animal structures, though in a less degree than resinous sub- 

 stances; and may thus be advantageously employed as a component of 

 media for mounting objects that are rendered too transparent by Balsam 

 or Dammar. Two cautions should be given in regard to the employment 

 of Glycerine; first, that, as it has a solvent power for Carbonate of Lime, 

 it should not be used for mounting any object having a calcareous skeleton;, 

 and second, that in proportion as it increases the transparence of organic 

 substances, it diminishes the reflecting power of their surfaces, and should 

 never be employed, -therefore, in the mounting of objects to be viewed by 

 reflected light, although many objects mounted in the media to be pres- 

 ently specified are beautifully shown by 'black-ground' illumination. 



e. A mixture of one part of Glycerine and two parts of Camphor-water may be 

 used for the preservation of many Vegetable structures. 



/. For preserving soft and delicate Marine Animals which are shrivelled-up, 

 so to speak, by stronger agents, the Author has found a mixture of 1 part of Gly- 

 cerine and 1 of Spirit with 8 or 10 parts of Sea Water, the most suitable preser- 

 vative. 



g. For preserving minute Vegetable preparations, the following method, 

 devised by Hantzsch, is said to be peculiarly efficient: A mixture is made of 3 

 parts of pure Alcohol, 2 parts of Distilled Water, and 1 part of Glycerine; and the 

 object, laid in a cement-cell, is to be covered with a drop of this liquid, and then 

 put aside under a bell-glass. The Alcohol and Water soon evaporate, so that the 

 Glycerine alone is left; and another drop of the liquid is then be added, and a. 



