CHEMICAL RE- AGENTS. 91 



This solution, which was first proposed and employed by Professor 

 Schultz of Rostock, is more convenient in its application than iodine 

 and sulphuric acid, and performs nearly the same services, while it 

 does not, like the sulphuric acid, destroy the tissues to which it is ap- 

 plied. It is prepared by dissolving zinc in hydrochloric acid; the solu- 

 tion is then saturated with iodide of potassium : more iodine is to be 

 added if necessary, and the solution diluted with water. 



8. Nitric Acid, or what is better, chlorate of potass and nitric acid, 

 as an agent to effect the isolation of cells. The mode of employing 

 this means, also discovered by Professor Schultz, is as follows : 



The object, a thin section of wood for instance, is introduced, with 

 an equal bulk of chloride, or chlorate of potass, into a long and moder- 

 ately wide tube, and as much nitric acid as will at least cover the whole. 



The tube is then warmed over a spirit-lamp; a copious evolution 

 of gas takes place, upon which the tube is removed from the flame, 

 and the action of the oxidising agent allowed to continue for two or 

 three minutes. The contents of the tube are then poured into a watch- 

 glass with water, from which the slightly cohering particles are col- 

 lected and placed in a tube, and again boiled in alcohol as long as any 

 colour is communicated. 



They are again boiled in a little water. The cells may now be 

 isolated under the simple microscope by means of needles. The boil- 

 ing with nitric acid and chlorate of potass should never be carried on 

 in the same room with the microscope, the glasses of which may suffer 

 injury from the vapours. 



Thin sections of vegetable tissue are warmed for half a minute, or 

 a minute, in a watch-glass : boiling is here unnecessary. The section 

 is taken out, and treated with water in a watch-glass. 



9. Oil of Lemons, or any other essential oil, for the investigation of 

 pollen and spores. 



10. A moderately strong solution of Muriate of Lime (one part 

 dry muriate of lime and three parts distilled water), for the preserva- 

 tion of microscopical preparations. This is applicable to most things, 

 even for the most delicate preparations, excepting starch. If it is de- 

 sired to keep a preparation, which is not to be retained permanently, 

 for some days, a small drop of the solution may be placed upon it, and 

 the whole put under a glass cover to keep it from dust. 



Lastly may be enumerated a pretty strong solution of Carbonate of 

 Soda and also of Acetic Acid; which latter, however, is more especially 

 useful in the investigation of animal tissues. 



To the above may be added a test for protein compounds. This 



