OF THE MICROSCOPE. 203 



on a water bath heated to about 125 Fah. The jelly then pen- 

 etrates every part of the preparation. 



When intended for use in very warm climates the proportion 

 of the gelatine to the other ingredients should be increased. 



HANTZSCH'S FLUID. Very beautiful preparations of delicate 

 vegetable forms have been prepared with this liqui.l, even the 

 coloring matter being left unaltered. It consists of 3 parts of 

 pure alcohol, 2 parts of distilled water and one part of glycer- 

 ine. The object, placed in a cell, is covered with a drop of 

 this liquid, and then set 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 to be added, and a 

 second evaporation permitted; the process being repeated if 

 necessary, until enough glycerine is left to fill the cell, 

 which is then to be covered and closed in the usual macner. 

 We have used this liquid with gratifying success. It is easily 

 prepared, is not difficult to use, and it gives very excellent re- 

 sults. 



GLYCERINE AND GUM. Of this medium Carpenter says: " For 

 many objects that would be injured by the small amount of heat 

 required to melt Deane's gelatine or glycerine jelly, the gly- 

 cerine and gum medium of "Mr. Farrants will be found very 

 useful. This is made by dissolving 4 parts by weight of picked' 

 gum arabic in 4 parts of cold distilled water, and adding 2 parts 

 of glycerine. The solution must be made without the aid of 

 heat, the mixture being occasionally stirred, but not shaken, 

 whilst it is proceeding: after it has been completed, the liquid 

 should be strained (if not perfectly free from impurity) through 

 fine cambric previously well washed out by a current of clear 

 cold water; and it should be kept in a bottle closed with a glass 

 stopper or cap (not with cork), containing a small piece of 

 camphor. The great advantage of this medium is that it can 

 be used cold, and yet soon viscifies without cracking; it is well 

 suited to preserve delicate animal as well as vegetable tissues, 

 and in most cases it increases their transparency. 



DEANE'S GELATINE. Before the introduction of glycerine 

 jelly, Deane's gelatine was a favorite medium, and we still use 



