i84 THE MICROSCOPE. 



many openings in a solid block of wood, and covered with a bell 

 glass to exclude dust, forms the handy little appliance known as 

 Ranvier's Necessaire, which I would advise every working micro- 

 scopist to provide himself with. 



It is to be hoped our cell with its fluid contents has been under 

 the friendly protection of a bell glass or inverted tumbler during 

 this digression, otherwise some of the dust always floating about, 

 and which is one of the microscopists most insidious foes, must have 

 found its way unbidden into the same. With a small camel's hair 

 brush or red Sable pencil, take up a portion of the starch which has 



Fig. iq. Ranvier's Necessaire. 



settled at the bottom of the glass and place it on the fluid in the 

 cell; it will instantly sink to the bottom, and must be evenly dis- 

 tributed over the same, with a small brush or needle point. A 

 cleansed circle of thin glass is now to be taken up by the forceps, 

 gently breathed upon, and one edge lowered upon the still soft 

 cement of the cell. When it is found to be firmly anchored as it 

 were, lower the other side gi'adually, so as to gently drive out the 

 excess of fluid without dislodging the starch granules, until the 

 whole cover lies flat upon the cell. Then gently with the points 

 of the forceps press it down upon the cement all around the circum- 

 ference of the cell, taking great care not to touch the glass where 

 it is unsupported by the cell wall, since, being elastic, it will yield 

 to the pressure, and a portion of the fluid will be expelled, only to 

 be replaced by air on removal of the pressure, thus compelling us 



