'774 MICEOSCOPIC EE-AGENTS. 



chloride and 3 of water make also an excellent solution for preserving 

 objects which do not contain starch. 10. Glycerine is the best pre- 

 servative agent for cells containing starch. 11. Solution of Canada 

 balsam (see Preservation of Microscopic Objects, page 783); and 12. 

 Turpentine, are most useful re-agents and preservative materials for 

 many dry preparations. 13. Nitric acid, used for separating cells. 14. 

 Dilute hydrochloric acid may also be found useful in removing deposits 

 of carbonate of lime. 15. Pyroligneous acetic acid. 16. A solution 

 of carbonate of potass or soda. These sixteen substances should be 

 arranged in stoppered glass bottles (excepting the Canada balsam, 

 which should be placed in a corked bottle), fitting into a stand or 

 box, so as to be of easy access ; and small camel's hair brushes, 

 pipettes, and glass rods, should be arranged beside these bottles, in 

 order to apply the fluid to the object. Lastly, the student should 

 provide himself with a small note-book of good drawing-paper, on 

 which he ought constantly to practise the delineation of the forms or 

 outlines of the objects seen, and he should endeavour to colour them 

 also when required. 



Numerous other requisites and appliances will suggest themselves 

 during the course of investigations, and especially such as will secure 

 cleanliness of the object, and of everything used in the research. 1. 

 One who has any regard for his instrument will never sufier it or its 

 lenses to be handled by those unaccustomed to their use. 2. The 

 microscope, when not in use, must be kept under cover, generally 

 under a glass shade. It should never be exposed in a chemical 

 laboratory. 3. Its lenses must be cleansed when necessary by soft 

 wash-leather, or a cloth which is used only for that purpose. The 

 cloth best adapted for this purpose is old and frequently washed 

 linen. 4. A separate cloth of a coarser kind is to be used for drying 

 and wiping the slides and covers. 5. Covers of a middle size, from 

 concave disks, such as watch-glasses, up to the size of a wine-glass 

 without the stem, or other bell-shaped jars, are also required to 

 protect the objects, if it is necessary to leave them for any length 

 of time. 



The microscope is used to best advantage in a room which re- 

 ceives its light from the north or west, or both. The light which is 

 reflected from a white and motionless cloud opposite to the sun is the 

 best that can be obtained. If gas-light is to be used, it ought to be 

 softened by passing it through a blue glass shade before reaching the 

 mirror ; but for exact observation, daylight is always to be preferred. 

 When observations are made at night a sperm-oil lamp is used, and 

 the light is transmitted to the mirror through a plano-convex lens, 

 called a condenser. To correct the unpleasant glare attendant on the 

 reflected light from an ordinary mirror, Mr. Handford makes a mirror 

 of thin concave glass, three inches in diameter, the back rendered 



