CHAPTER XIV. 



REAGENTS RECIPES. 



LITTLE now remains but to notice the action and pro- 

 perties of some of the various reagents used for micro- 

 scopical purposes, and in order to put them in something 

 like order, they are divided into four classes softening 

 agents, dehydrating and hardening agents, bleaching and 

 oxidising agents, and solvents. 



Softening Agents. One of the mildest softening agents 

 with which the microscopist has to deal is acetic acid 

 diluted with four times its weight of water ; it renders some 

 tissues quite transparent, and used in conjunction with 

 glycerine serves for sending insects for dissection to long 

 distances. Acetic acid dissolves phosphate and carbonate 

 of lime, but does not dissolve oxalate of lime, and neither 

 has it any action in the diluted state upon any of the 

 varnishes or cements in the general use of the microscopist. 



Glycerine is a fluid of the greatest use in microscopical 

 research, particularly as an agent for preventing the drying 

 up of tissues. One part of pure glycerine diluted with 

 nine parts of water produces a fluid of the same density as 

 sea-water, and this strength is a very handy one to use. 

 Contrary to the general opinion, cells filled with glycerine 

 do not necessarily leak, it is only when objects have been 

 slovenly mounted in this medium that such a mishap 

 occurs. 



The alkalies, potash, soda, and ammonia, are somewhat 

 alike in their action upon many substances, ammonia being 



